[ASalazarMX]

Compare it with tax law: lawyers, legislators, and many other people dedicate enormous amounts of time to create tax laws, and still tax evaders (hackers) find loopholes to exploit. Those loopholes are the law's bugs.

One could argue that those loopholes are left intentionally (back doors), but even if all actors were honest, bugs would still happen from time to time.

Computer code has even more bugs because it is produced massively and quickly, without the bureaucracy of tax code. Anyone can create an awesome application/library/framework/etc., and share it freely with the world. People end up using these projects as stepping stones for their own projects, creating a complex layered cake where bugs can hide for years.