People don't come and watch the matches. In county championship games the crowd sometimes doesn't even reach 3 figures for a days play and grounds are nearly always less than half full.
The structure is just crap. There are way too many games, one day cricket and first class cricket is on at the same time, games don't always start on the same day, and the schedule is way too crowded, with players hardly ever getting a day off, leading to injuries.
If you were to actually look at a full fixture list, you'd see that it is just a mess.