People who don't go very often.
People who live abroad (and don't go very often).
People who pay on the gate.
People who get others to buy tickets for them.
People who share ticket purchases across the family or friends.
People who buy from the ticket office.
So yeah, a fair few I'd think.
The people who dont go often, outside of not being arsed or who are just jumping on the band wagon may also include:
People with Work constraints,
People with Health issues,
People with Financial Constraints,
People with very young families (adds to the financial challenge!)
No doubt many more..
Basically loads of reasons outside of "not being a proper cov fan".