Maybe I'm uneducated here, but wouldn't this just commoditize the products of companies? Would it disincentivize them from creating their products in the first place?
In more general case, you don't pay for the client software (or web page), you pay for the service provided trough it, so it should not matter if you use the service trough different client.
Of curse, many of these new clients do provide options for getting around the data collection or make it possible to block the advertisement, and that makes the companies so strict about who makes clients and how.
Essentially, if competition entered the market, Apple (and co) aren't going to give up, they'd be forced to innovate in order to retain market share.
If individuals (like me, some random on the internet) were permitted to create competing services on top of hardware and software that exists, you'd be running SteamOS on your MacBook, you'd be plugging your phone into a USB-C dock or lapdock, you'd be able to export data from your health tracker so you can buy a new one and keep your existing data, etc.
By contrast, the status quo of permitting corporations to attain functional monopolies by making it practically impossible to compete is a far worse outcome for the general consumer.
Also, when you consider that the EU is looking at cutting their reliance on US technologies - they are literally not going to make a MacBook or iPhone in this decade - but if Europeans were allowed to install their own software on these devices, the road to sovereignty gets a whole lot less impractical
Also, as stated below, as long as you don't prevent YouTube (or similar) from making money from ads (ad blocking, etc) - there is no reason to not allow you do to this.
Where do you get those silly ideas?
We want this. Software and other modern tech desperately need this! How many companies are stuck with an absolutely terrible suite of MS products because you can't easily rip out and replace just the IM or videoconferencing part, for example?
Its bad for vendors.
Why would vendors do something that is bad for them? HN is full for people talking about how to create a "moat" for their products. Why do you expect hardware vendors not to want to do the same?
of course they want the moat - the point is that society as a whole should force them not to have a moat. Ala, they should not be allowed monopolies.
Unfortunately, this sort of legislation has been lacking recently, and in fact, has been failing even enforcing existing ones from yester-century.