Maybe the 7 other games in April are considered more important or already paid for or committed to.not all all, i have sympathy with anyone who cannot afford it, but it's 30 quid and a free travel if you really really wanted to go, show me any day out for less than 30 quid.
The £30 tickets are in different time zone and there are 4 singles left, so not an option for most people.
The bulk of unsold tickets are £65 in the 3rd tier for a game where we will play a weakened team, as it won't be a priority for the manager with the games around it.