I don’t think this is an issue – not unless you try to scalp them on their prices anyway.
During the years I’ve been trading I’ve been put on dealer referral, in two spreadbet companies, and so I moved on, but my account wasn’t closed. If you win, you are not ‘necessarily’ an unprofitable client, it depends on how the spreadbet firm operates. It might depend upon how you trade – if you make a million pounds a year scalping, they probably won’t want you because hedging/shadowing your trades might be impossible. If you traded longer term, chances are it wouldn’t be a problem
If you utilize spread betting wrongly you are likely to end up a loser or become an unwelcome guest at the party. Spread betting is not designed for people to deal hundreds of times throughout a trading day trying to capture miniscule moves. In reality spread betting is very easy to understand but it is too easy for greed to take over.
Considering many spread betting firms are offering spreads wider than the real market, then all they need to do is hedge your trade, and they’re making money from you irrespective of whether you win or lose. Whether they do that is another issue..