There are a couple of areas that have tried to DIY, with limited success, they usually simply don't have the technical knowledge on staff. I've been surprised myself at the breadth of technical turf I've had to cover to create something that works reliably and simply. For a reasonably technical software engineer with a bit of hardware experience, it's not a big deal, but for everyone else, it's too complex a problem.
One of the really interesting problems I had to solve was reliably figuring out which trail the grooming equipment was traversing. Unlike roadways, the GPS data for the trails is typically either non-existent, inaccurate or just plain wrong. Cleaning that up is a bit of effort for each ski area. In addition, ski trails are often in much closer proximity than roadways, which combined with GPS error margins, means that I had to do some fairly gnarly stuff to avoid jumping between nearby trails constantly. It looks simple enough on the surface, but it required some real hair-pulling to get working reliably.
Contract negotiations with cell-network providers weren't much fun either. Many ski areas are in pretty marginal cell-network coverage regions, so finding devices that behaved well in that environment was critical (in addition to handling very cold weather, i.e. -40F for 8 hour stretches). The grooming staff are typically completely non-technical, working weird shift hours, etc, so the system has to be completely hands-off after installation. Finding a device that would do that, handle the harsh environment and be properly certified to operate on the north american mobile networks was no easy task.
