I take it your a good boy like me and always paid the balance in full on time
I think you will find that most companies are trying to get rid of those customers who NEVER pay charges.
I used a Marbles card to help rebuild my credit history after years of been a daft cee you next tuesday with money / bankruptcy.
Started off with 1200 quid limit.
Always paid it off on time so the craft buggers dropped my interest rate and more then doubled my limit.
After a couple of years of no charges, it was dropped down to 500 quid
Doesn't bother me if i'm honest, It does the job if I need another 50 days to save up and i've got a PayPal credit which gives 4 months interest free if I really have to buy something and need a little longer
With my Marbles card the default for PayPal anyway, as long as I use my brain, I get upto 6 months interest free on everything