Inflation is less obvious that outright confiscation, and so it's easier politically. That's the reason they prefer to finance their spending by inflation rather than taxes. People notice a big chunk of change missing from their paycheck or bank account and blame the politicians, but people either don't notice inflation or don't lay blame where it is due.
Secondly, raiding bank deposits undermines confidence in the banking system. If the government starts seizing bank deposits regularly, they'll cause a bank run and then the game is up. They don't want that.