Alternatively, 98% is plenty . If your business plan requires you to capitalize on more than 98% of the market, it's already a failure. It'll never happen. As always, it's an "it depends" situation. If your userbase is largely luddites, then maybe you need to support 10+ year old browsers that can't be updated. Otherwise, you can probably just worry about people who are using computers new enough to actually update t…
Unfortunately some business are critical where is not an option or very expensive for someone to not use it. For example, Uber, a Visa immigration website, low cost air carrier booking site, etc.
As long as it’s credibly offered without too many caveats.