It's a big mistake for clubs to send players without making a profit and the clubs that do this are big clubs but they act in an amateurish way. Some clauses should be added to the contract in order to prevent behaviors that harm the club in star transfers. Big money is made under the name of signing money and clubs are prevented from making any profit from this situation. I'm not making an assessment of whether this behavior is right or wrong, but agent fees and signing bonuses prevent clubs from generating revenue.
It seems that Liverpool will not get any income from these players. Some clubs demand very high transfer fees from their players and never lower them. It is surprising that the club took this decision despite knowing that the players will leave the club after a year.
If a club does not put a player up for transfer, it means that it expects to renew the contract with him, but sometimes it happens that they are unable to agree on new terms of the contract with the player, when the player wants to receive more payment, or a longer contract and the club is not ready to give them such conditions. In this case, there is a risk of releasing the player as a free agent and, of course, this will be a big loss for the team. Sometimes this happens, but more often the teams manage to come to an agreement with the players.