This spelling error is not a one-off mistake. It's repeated on another sign on the front of the building, and I noticed it's even on one of their trucks. I suspect that nobody has ever pointed it out to them.
Maybe I'm being picky, but it seems to me that if you make a spelling mistake like this on your signage, it suggests that you don't pay attention to details. When I hire someone to work on my plumbing, heating, or air conditioning, I want someone who wants to get the details right, because that means the work is likely to last. Maybe that's why we've been so happy with Marraccini Plumbing Heating & Cooling and Steve-the-plumber who has worked so much on our house.