If you think about it, we are saying more or less the same things here. LOI and or cash is a contract in the wider sense of the word.
No I have not lead a charmed life and I have been cheated by an agent and I have had the usual difficulties with people for whatever reasons, as have we all! In fact I have been cheated twice by agents (I forgot the other one) and on both occasions we had proper formal contracts with them.
My point is that business is all about trust and having a contract or other piece of paper does not always help. If you look at the two big rock-star examples I gave above, both had contracts and as a direct result of sticking to the letter of those contracts and insisting on their rights under those contracts, they kissed their careers goodbye (they were unbelievably rich anyway).
Of course I realise that a big place like the Abbey can't run three main rooms, several production suites and over a thousand customers a year without masses of structure and organisation and even for the larger agencies, that still means booking forms, etc.
But I am not a multi-room, big city opperation. In fact, very, very few people are in the studio/engineer/producer scene. So after getting screwed over under contract, I havve since relied on my nose instead and it has worked.