However, I can see another counter-argument to my claim: not every consumer has specific requests for the product they're buying! Sometimes people are just not sure what they want. In that case, yes, I can agree that customization doesn't help. Moreover, having a limited set of pre-defined products helps to educate a consumer on what their options even are.
So, if a large part of consumers are the ones that don't know exactly what they want, then yes, you're right. I guess the distribution of “know-what-they-want” vs. “don't” depends on the product, although I think generally it tends to be that most people usually don't know.
Anyway, thanks for the good argument! Thinking about other products and industries, as cars, really helped, I missed that.