My knowledge with Windows is a few years outdated but the way I recall it is that basically every DC by default is a DNS server (or at least the first DC that gets created) - because you need a name service if you want a useful Intranet.
So every company that has AD probably has a Windows DNS server - which is kind of like every bigger company.
Hope someone can confirm or dispute my info with 2020 hands-on experience.
Yep. Most of the small companies I've seen just use the Windows DNS servers because they need them for AD. You can set up separate DNS servers and delegate AD's domain to the domain controllers, but then you're maintaining additional DNS servers.
And besides, most of the small companies I've seen vastly prefer a Windows GUI than (e.g.) configuring bind on the command line.
So every company that has AD probably has a Windows DNS server - which is kind of like every bigger company.
Hope someone can confirm or dispute my info with 2020 hands-on experience.