Unfortunately that still leaves out a ton of users. I know that's a tiny percentage, but tiny nonetheless. The shop i'm heading to soon has a small number of clients (<5k, each being very important), but with many using
ancient systems. IE8/9 iirc. We use Table layouts for our "old compatible" product, and i don't think we'll ever move on from that. Some clients just refuse to update it seems.
Luckily (for my sanity) we have a "new age" product that we can use responsive layouts for.