I'm a one-man, mobile-only shop handling both business and residential clients and have been full-time since 2003.
Over the years, I've checked into various business-related insurance, but never really felt it was needed. The only exposure I've ever felt was when I had to take a customer PC back to the shop - what if I got into a car accident, what if the PC developed a problem due to road vibration, what if I dropped the PC taking it into the shop? "What if ..." can drive you crazy.
For me, it's simpler to self-insure. The business keeps a small chunk of money set aside for emergency situations and I could tap into that even if I had to totally replace a customer's PC that I accidentally physically destroyed.
Now if I had a physical shop, that would be a totally different story.