It's most likely the escrow thing that stops a lot of people that may even be interested. Newbies basically always, as a general unwritten rule of Bitcoin Talk Forum, need to use escrow as they have no trust or any history on the forum.
That is probably true, which is why I am actually fine with using escrow at this point, as long as I can also be a part of choosing which one to use.
Also, there are probably bots or methods which to get this amount of accounts quickly with no risk of them getting taken back.
Sure, you could do that. But the thing is, when you create a new Steam account these days, it will have a limited status. To remove the limited status you will still need to spend at least $5 for every account to able to use all features of Steam.
My 100 accounts already have full access to all of Steam, and their profiles are already set up, and they have games, and levels.
And no, there is actually no risk of these accounts being taken back either, as I already explained these 100 accounts have not had any phone number registered to them, if a buyer registers a phone number to them there is zero chance for anyone else to access the accounts ever again.