A lot. There are so many old corporate web based apps that only work in comparability mode in edge.
We have one customer that we provide virtual desktops for that have to run edge because that is the only browser that will work with their traffic control systems.
Edge has an Internet Explorer mode, which is just running IE with Edge wrapped around it. They're making it harder and harder to use, but they know there are big spenders that will just stop updating if they ever try to take away IE completely.
Source: I work in Healthcare IT.