That is only of you treat rocketry as a hobby and not a science.
It you treat amateur rocketry as a science where everything is optimized, you will choose the platform that is the smallest, most lightweight, has the lowest power requirements, and has the fewest components to reduce likelihood of failure.
The Pi is bigger, heavier, requires more power, and is far more complex without providing any benefit in return. Furthermore, you don't have brownout or watchdog control, so even if you can recover from a failure, you still need to wait several seconds while you re-boot Linux, whereas a simpler MCU will be back in a matter of microseconds.
And finally, it is entirely possible for the hobbyist to understand the operation of an 8/16 bit MCU solution end-to-end and actually construct the board from scratch.
I am not saying you cannot use the Pi, just that it is a very poor solution no matter how you look at it.