Well there's all sorts of issues. But what it essentially comes down to is that evolution works in tiny steps, not in great leaps. When "trying to achieve" goal

Well there's all sorts of issues. But what it essentially comes down to is that evolution works in tiny steps, not in great leaps. When "trying to achieve" goal X, adding a tiny bit of complexity is simply much more likely than a simplifying "refactoring". And then in terms of the biology itself, you will run into things that we might think of as "complications" but which are actually for the sake of redundancy/fault tolerance, etc. I remember watching a series of biology videos where a particular messaging pathway was explained. It had at least 5 or 6 proteins. But then the lecturer described that by having so many proteins in the chain, the messaging is exponential. So what initially might seem like a complex way of sending messages is actually an amplifier!