Unlike ground systems, when working with avionics there are certain parameters that are considered more important than what would be on the ground. This is obvious within weight for several factors, minimum weight for a couple of reason, optimise space and weight for other things, optimise fuel.
Be able to work in several different operating environments when working with things such as operating temp range, acceleration, shocks, vibration, humidity range and electro-magnetic interference, a lot of these thigs wouldn’t need to be considered to this extent. When working with avionics there is little room for error, unlike a car if there is an issue there is a good chance of coming to a gradual stop, unfortunately planes do not have this luxury in most situations, meaning there must be a high level of reliability, safety checks and integration.
Also, if a part does fail, there is normally a back up copy of that part that can be integrated into the system without failure of the plane, resulting in safer travel and a back up plan to help mitigate the problem.