Google's search results algorithm heavily penalizes sites with two separate desktop and mobile versions, and rewards sites with only a single "responsive" version that works on both desktop and mobile.
Google penalizing your business is very costly. Thus, everyone's moving toward single, "responsive" sites for all devices, desktop, tablet and smartphone.
Unfortunately, they tend to work okay on phones, semi-decently on tablets, but on desktops they're usually crappy, and look like a smartphone version stretched to fit a giant desktop monitor, with buttons that are way too large (because everything has to be 'touch-friendly' now, and fingers are far larger and less precise than a mouse pointer), and usually text that's way too large, too (because smartphones have tiny screens, and using desktop-sized text on them would make it nearly unreadable without pinch-zoom, which is a HUGE usability/UX no-no for sites that will be viewed on phones).
I don't like it, and neither do lots of other web developers and businesspeople, but it's the way of the world, thanks to Google. Not much can be done about it.
One benefit is a single codebase to maintain, not two, which reduces effort and web developer labor needs, which is great if you're the business, but not-so-great if you're a web developer who got laid off because of it.
It's also no fun for desktop users, who are slowly seeing site after site turn from feature-rich with useful sidebars and appropriately-sized buttons and text, to feature-stripped sites with no sidebars, needlessly giant buttons and text, etc.
.
Pudding Mittens wrote: