For one thing, it's the very definition of anti-competitive behavior. It's bundling of services in a way that allows them to leverage their market advantage. Even in theory, markets only work if there's intense competition in each separate market. But the moment one actor can leverage their strength in one market into another, competition goes away and the advantages of economies of scale become insurmountable.
Worse, it's just impossible to negotiate in good faith in this way. EULAs should already be unenforceable in a lot of ways: many are for products you purchase before you sign anything, which is the definition of an unenforceable contract since it is requiring someone to negotiate to use something they already own meaning there is effectively no consideration at play, and most are so labyrinthine and include so many terms that can be changed any time in perpetuity that there's simply no possible way that they could be negotiated in good faith. Insisting that someone simultaneously agree to several of these already-questionable EULAs is laughable.