What determines which services are subject to checks?
On the "local" services into London I would reckon I have never been subject to a ticket check on what could be considered to be the usual peak commuter trains (arriving before 9, leaving after 5).
When I have either taken a later train in or earlier train home I can almost guarantee there will be a ticket check (and yes, usually involves at least one or two "conversations" in the carriage).
I can only assume the ticket inspectors don't relish fighting their way through the overcrowded carriages. Or perhaps they like a good breakfast and early tea-time
Given the regularity of apparent fare dodging at other times, the numbers of people occupying 1st class (I may be wrong but...) and given that it is currently possible to arrive on platforms 13/14 (as most local trains do) or 10/11, go straight to the H&C line and "touch in" without any barriers there must be a potential gold mine waiting to be uncovered.
It also amuses me that the door from the ticket office to platform 4 at Twyford is usually manned in the mornings and everyone is asked to show their ticket but the the large double doors further along are usually open and the side gate at Platform 5 is always open and both unmanned.
Thank goodness we live in a world where we are all honest folk.