There was this article from TNW that brought to light how some companies (e.g. Airbnb, Groupon) only build or optimize for Google Chrome. I thought this problem was left back in the Netscape/IE5/IE6 days, but many developers in the comments actually expressed that this is something that they're proud of doing.
I personally think that it is the job and responsibility of being a web developer to build for all browsers (within reason), especially now in which it has gotten so much easier to do. Even if a certain feature is not available doesn't mean that you entirely drop support for that browser -- you just offer a slightly different experience (or polyfill the functionality).
I did a podcast episode on this today and thought it'd be fun to ask the Hashnode community as well. So, do you only build for one browser? If so, what's your reasoning behind it?

Marco Alka
Software Engineer, Technical Consultant & Mentor
At work, I build for the corporate standard, which currently includes 3 desktop browsers and two mobile ones - at specific versions. I am happy about that environment.
However, when building for the internet, I usually tend to support IE11+ era browsers (using caniuse.com), because out of habit, many people still open their IE on Win10. All browsers of this time are very capable and I can use many modern features. I really hope, though, that the usage shifts more towards more current browsers, especially away from IE :)