Speaking as an accomplished fence-sitter....I'm told that the Cambridge lot don't get the use of their gallops whenever they wish, as the huge numbers in training there preclude that. Okay, I can understand that, but now that the AWT is in action, that shouldn't be an issue.
Clearly, the need/desire to sell drives most trialists I should think regardless of the above comment.
Locally? the tracks and the rules inherent mean that no more than two are supposed to be worked upsides. That doesn't provide suitable education for a novice in my book. You can't work your baby tucked in behind a couple of older sorts to get a line on him and teach him. In our day, JB, the the boss may give a youngster a couple of quiets before deciding that it is ready to 'have a go' ..again, that is frowned upon now... and with no form you have no ratings points so can't get a start. A trials win does give you that.
Also, the tracks available may be awful so you go somewhere else to get a nice gallop into your horse. The cost is draconian all the same.
I've trialled some more than I would like, because barrier manners, for example, need polishing - yes we do have jumpouts but only up the back straight as a rule, and from the old wooden gates. Apply raceday conditions and overhead gates and things can be very different as we found out with a recent barrier drama.
As for the track rider comment - it may well be that it is a chance to get jock on as opposed to your fledgling apprentice, for an opinion and education. There is no doubt that a quality rider is worth at least fortnight's work to your novice.