You are right that computer generated proofs are often tough to understand, and that understanding is often the intended goal of writing a proof. But proofs can be useful for reasons besides human understanding, especially so in engineering. For example, when a browser establishes a secure session with an encryption protocol, the reason it is secure has to do with the difficulty of finding a proof that eg certain numbers factor, but no human cares about this proof. As another example, a compiler can use a proof that a program is type correct to optimize it, but humans would not find such proofs interesting at all.