I thought cheques required a bank to use?
Depends on the kind of cheque. Belgium has five different kinds of cheques, some of which must be deposited into a bank account. Some cheques can be cashed, in which case you do not need an account and do not need to patronise a bank. You are purely a burden to them in this case. In this case, the cheque is a cash access mechanism that does not require licking any boots.
Cash is the only option which doesn't.
Cash gives the greatest autonomy but receiving a salary in cash has been banned in Belgium for like decade or so now. So the paper cheque is currently the sole mechanism for autonomy in Belgium.