Different parties involved.
For me, it makes the whole idea of a day out at Wembley now seem less special.
By all accounts they are at least paying the going rate for Wembley, unlike West Aaaam, so I don't have too many complaints. Wembley is a massive waste of space and is always whoring itself out to try and pay for it's ridiculously bloated expense, so it makes sense to be available to club teams. All it does though is it completely undermines building it in the first place