To say Raleighs failure to produce a decent entry level bike is the singular reason most kids didn't progress utter nonsense, I've read this sort of BS on forums for years, most of the kids who were going to progress further did and those that didn't, didn't for a variety of reasons, lack of cash being the main one.
Yes the basic models were poor, Raleigh pinched frame design from Raleigh USAs Rampar, compare a Rampar R10 from 1976 (influenced by the Redline Squareback etc) and Raleigh Mk1 Burner from 1982 they are virtually the same bike. They were cheap to make as most used hi-ten steel and they tweeked the seat-tube to accept the seatposts from other bikes they made in the UK. Unfortunately it was a very out dated design dating from the mid 70's but it was tough and that's what Raleigh would have wanted as they had a reputation for selling quality bikes that lasted. I dare say Raleigh knew the vast majority of these bikes would be very unlikely ever to hit a race track and far more likely to hit the streets as general transport for going to school, paper rounds and the like so they had to be tough and they bloody were.
If there hadn't been a Raleigh Burner a lot of kids would never have got into BMX in the first place.