It's not uncommon, IMO - you have a bit on one, bit on another, transfer one over to get 0% balance transfer, buy an telly, and before you know it, it's a big chunk out of your monthly income. The companies still offer hikes if you are a good payer - one of mine offered me a borrowing ceiling of £11600.
One of our card companies contacted us last year and told us they were reducing our available credit (by quite a lot) - we thought that was sensible on their part, it reduced their risk and ours.