It isn't arrogance. A good lawyer has a huge advantage over your average layman in a contract negotiation, and shooting fish in a barrel isn't sporting. You and I negotiate a lot of contracts, so we're good at it, but not everyone is, by a long shot.
A lot of my gigs are smallish, just a week or two worth, so I can't afford to have a lawyer involved. The one time so far that I needed one (for a royalty deal) it cost about $12k, but if it turns into a product, it was well worth it.
Expert witness work can be fun if the technology is interesting, and it exercises a different part of the brain from design. It also pays roughly half again as much per hour, and if you pick the right gigs, you can help justice get done.
A couple of times, I've had to tell clients quite bluntly that the other side is actually right on the facts. Some don't like that, but it's in their best interest not to pursue a matter that they really can't win, and the sooner they find that out, the better for them.
Cheers
Phil Hobbs