And yet, technology stacks aren't exempt from social and economic dynamics. Technology stacks are tools, means to a wide variety of ends. And as such, if they are freely available, people can and will use them for whatever purpose or need they seem fit.
As such, linux is just as much a product and a service as it is a technology tied to very real markets and niches. And it with that come the exact same concerns you'd find in any other market.
Your observation is totally correct: there are tons of distributions and there is plenty of choice and people don't care.
But that choice is far from granted, and it's not an argument that deprecates questions about moral responsibility: Are companies providing a service/product entirely responsible for the consequences? Or are customers entirely responsible for their own choices and behavior? Or is it both?
Let's use an analogy to demonstrate. Bread is a great example.
The vast majority of people eat bread daily. And so there's a huge demand. But the market has consolidated in some places and so many people end up buying bread from retail chains. Sadly, such bread is a processed food and contains many ingredients that aren't that healthy such as emulgators (E-numbers), or loads of sugar.
You could argue that people still have a choice: You could go to an artisanal baker. Or you could bake your own bread: the recipe isn't that difficult and requires few raw ingredients. So, why aren't people doing that when they know retail chain bread isn't good for them? Three reasons: because artisanal bread is expensive; it's a different shop from a centralized retail shop and making decent bread takes time and skill. Consumers simply calculate cost/benefits: buying cheap bread is far more convenient in the short run, even though the long term consequences may cost more.
Okay, so how does that hold up with Linux? Same thing.
Ubuntu is huge because it was successful in it's marketing early on; and it did a bang up job in creating an effective onboarding experience for new linux users. You can argue about their design choices over the past 15 years, but in the end, they have been ahead of the competition when it comes to tapping into a new generation of users.
As time went on, what you see is that the Ubuntu community has spawned a huge volume of documentation: tutorials, videos, stackoverflow posts,... Google "how to install sound drivers in linux" and your first hit will be tutorial for Ubuntu. Whereas trying to find the same information for lesser known distributions might be just a tad harder.
And that's what makes all the difference. Convenience. If you spend an evening trying to fix your damn audio after first installing Slackware, and all you find is Ubuntu tutorials, you will likely just switch over to... Ubuntu. Especially if you aren't particularly interested in the design philosophy of Slackware, or who these Canonical people are anyway. You simply want to listen to your favorite Spotify playlist, right?
So, the issue here is that both retail chains and Canonical understand that the vast majority of people simply want convenience and they will easily choose it over principle or their own self-interest. And so, it's extremely tempting to exploit that.
The question then becomes whether it's morally right to tap into that and take more from your customers or users then what they are bargaining from. Especially when they aren't really aware you're doing it. Either by using ingredients that aren't prohibited, but clearly unhealthy, or by using techniques to gain more insights about their behavior. Especially when everyone sells them "Linux doesn't do that unlike Apple, Google or Microsoft".
And so, ever more people will keep choosing Ubuntu over other distributions, even when they do have a free choice.
The mere existence of a choice isn't a defining factor at all, it's everything else: available tutorials, number of users, onboarding experience, how quick they can get things working and so on.
Tis where the discussion does turn political. The public space is regulated through laws for many reasons. But such rules and laws aren't static. They can change through political discussion and ever changing power balances. And so, consumer protection laws exist not just to protect individual consumers, but also to ensure that large, unintended second order effects of new products and services don't cause shocks that might derail an arguably stable society.
If retail chains are free to add more and more unhealthy ingredients to their food products because that clearly drives costs down and attract more customers, the societal cost will be an increasing number of people who suffer from health concerns linked to consuming those products. Not because people don't mind their health, but because convenience forces them, and the alternatives are simply too costly.
By the same token, if companies are free to build in all kinds of telemetry sending scripts, that won't stop people from using those products as they prove to be really convenient. But the societal cost will be that private enterprises are able to derive very accurate profiles about who we are, and what we want, and use those in ways that don't align with the interests of users of their software.