That's because they care about their users' security.
I think all aspects of that question were discussed in my other thread as well.
I don't want someone to care about my security because I am able to do it myself very well and also because it is a part of my job. Now, what I care about is security of the exchange I am using and I would like to be sure 2FA is not all security they have.
2FA is an extra measure that makes every account harder to get hacked.
2FA is only a user side security and the way how users protect their accounts is their own responsibility.
Exactly. That's why they make it mandatory. The regular user is usually dumb and lazy, so they don't enable 2FA because it's an extra step and takes extra time to login. When it's mandatory, less users get hacked and they get less useless support tickets.