[oatmealsnap]

15% is most likely too much to ignore. Most web developers have had to support IE11, which is at like, 3-4% tops.

[DrammBA]

I think the bigger problem is corporate environments, in my company, our B2B application sees IE11 usage at around 20-30%.

[dhosek]

This. Hell, most corporate users are still using Windows 7 (I try to avoid working some place I can't have a Mac, but despite Windows 8 having been released in 2012 and 20 in 2015, I have never seen either in a corporate environment).

[dwaite]

It is best to make your own decisions there based on some telemetry tbh. It will likely depend on your demographics but also upgrades may depend on your business model. For instance, you may be motivated to upgrade if you realize users who are on older iOS versions don't generate revenue.