For some reason, most shops don't even have/use tools like that, and still use the old school level method. Not sure if they don't know that it exists, or if they just don't want to spend the money on one? If I owned a gun store and offered that type of work, I'd have one in a heartbeat. The level method will work ok, and get you very close, but after pulling scopes (still mounted in the rings) and tested the plumb on the Dead Level, they were all slightly off. So, that right there was enough justification for me having spent that money on the Dead Level, especially to know that my level setups weren't quite as accurate as I had thought.
I've replaced the traditional dovetail base/ring setups on every single rifle I own. They now all have pic rails with high-end rings. So, for me, the Dead Level is worth every penny, because I can use it for every scope on every rifle I own.
If you have multiple rifles, or building a custom rifle, and want to learn to do your own work, buy some good tools. One of the best investments is the Dead Level, if you plan on shooting LR. Plus, self-reliance and not having to rely on a shop, makes you more independent, and will help you build more knowledge.