Steam does this as well. Even if you add your phone number after a lot of nagging, Steam still keeps bothering you to install their Android or IOS authenticator software (even if you can't). I wish Steam would consider Fido U2F as well, but getting through to anyone who can influence this at Valve is nigh impossible.

It seems to be the industry status quo now to assume that everyone uses a smartphone running either Android or IOS, and that everyone wants to use that device for authentication. Meanwhile the tech giants (especially those involved in advertising) probably like having that nice unique alphanumerical identifier for your profile — it tends to be the same for all services you use.

I really hope Fido U2F becomes a de facto alternative for 2FA.

Yeah, I just ran into something similar a few days ago. Every once in a while I used to go through all my trading cards and bulk sell all my duplicates for a few cents each, but apparently now they require you to use some combination of SMS and mobile app authentication to post anything on the market. Clicking through the confirmation email they send you isn't enough on its own.

So now I just don't bother with trading cards at all.

My experience exactly. I used to sell those silly cards the moment I got them, just to get a little extra balance in my Steam account for the next purchase. Now I just ignore them; selling them is way to much of a hassle to be worth the €0,05 you get for a card. (Who buys those things anyway? Weird market.)

Steam, at least, does not seem to have a issue sending me emails. Sure it annoys me to use their app or whatever, but i can choose to only receive emails. Which is really all i actually want :)

But i agree on everything said

It's protection against bulk account creation. Getting a phone number costs money, so requiring a phone number makes it expensive to get 1000 accounts.

Phones are ubiquitous enough that very few customers have to pay this cost.

Obviously, this reasoning doesn't (and shouldn't) extend to using phones for authentication.

Yeah, after writing the article i also realized i dont mind verification actually. As long as they support whatever carrier i currently have. Its authentification that i bother with. (As in i have a phone number, i want internet on my phone, but i change it often monthly)

Also services like Twitter that allow any rented SMS service and multiple accounts for each number this seems not be the reason why they ask for a number.