It's not a selfish act although it sounds like it is to others.
It is also for your health physically and mentally. Physically, binding can be really damaging to the lungs and ribs and cause breathing problems, it can cause problems with posture, back aches, etc. Mentally, it can make you depressed, unable to look in the mirror, cause issues in social situations such as changing at the gym or swimming. I'm sure the list can go on and on, and being unhappy without surgery can be unintentionally be dumped on to other people around you and that isn't good either.
It is no more selfish than people getting braces to align their teeth.
Hope that makes sense.