You can also rely on them to share tools. When you're on your own, does it make sense to buy the numerous tools that you only use once in a blue moon? Now I have to decide if I want to buy or rent them. Well if I'm going to go that trouble I can just pay someone to do it too.
You can rent some tools. If nothing else I often justify a good tool because if I hired someone the pro would have the good tools. Typically the first time I do a job myself I lose money on tools - but the next time I have that tool and so I save a lot. Of course over the years I have a good idea what tools I'm likely to use.
