The very point is that some of these mining coins are looking for ways to siphon money from people. That's why I hardly partake in them because this same act of asking for Ton as a way to be eligible for mined coins
It's clear that many of these projects just want to steal money from their users, instead of having to burden users with 0,5 TON in transaction fees, why don't they follow the path that the big projects do, namely by partnering with an exchange that will list their token, so that later transfers can be done off-chain.
Maybe because they think everyone is doing that already and they think people already figured that tactic out, so they are trying to be different even though this trick is not new either. If they follow what you suggested there, users will still have the burden to pay for the transaction fees and in fact it can be a lot. So users will like what they have done their better, not until they realized that it was not legit.
There are still legit projects though that can work the same as that. If you mean, that they can only earn 0.5 TON and it looks very cheap, you are wrong with that. First, they are not only earning that on one to two users but if many are doing that, combining each 0.5 TON can already go a long way. Secondly, they might have access to the users whole wallet once they initiate the transaction, so they can steal more money.