There are two kinds of motivations and rewards:
Intrinsic – you get internal rewards like fulfillment, enjoyment, feeling you accomplished something worthwhile, like a kid in a sandbox.
Extrinsic – you perform to get an external reward – a trophy, money, a higher position on the chimpile, a bigger this or that, like a dog doing tricks for a treat.
Many parents urge their kids to pick something secure, professional, well-paid and prestigious. When you succeed on their terms, they get is those sweet intrinsic rewards: they did their job as parents well. They are proud. It is satisfying (for them.)
So, what do you get? All too often just the extrinsic rewards: success without satisfaction.
NOTE TO PARENTS: why not support them to have both?