Bank rate changes attract rate chasers. If their current bank rate is not as high as a competitor's offering, they'll move.
Rate chasers earn good returns on their savings. However, monitoring bank rate movements takes a lot of time. It is more likely to pay off if your savings are large, and for many people it's not worth the trouble.
Moving for a better bank rate may mean that money goes a few days without earning interest. The transfer process may take time. You have to factor this loss of interest into bank rate differences to see if a switch is wise or not.
In general, you can earn competitive returns if you change banks about as often as you change your toothbrush. Diehard bank rate fanatics switch more often (again, it only makes sense for large balances). Switching less often is okay, as long as you don't leave meaningful money on the table.
