Responsive design isn't about looking good on phones.
When your site adapts to different screen sizes, you're helping people who rely on assistive technology. Zoom features become more useful when layouts don't break at high magnification levels.
Thinking about different screen sizes naturally creates better accessibility.
Consider how someone with motor difficulties uses a tablet in portrait mode. If your layout is fixed, they're forced into awkward scrolling. Buttons become impossible to reach. Responsive design fixes this.
People with visual impairments often prefer larger text and specific colour contrasts. A responsive site lets them customise their experience without breaking the layout. The content stays readable and functional.
People usually confuse responsive design with mobile-first design. They often go hand in hand, but they're actually different things.
Responsive design is about making your site adapt to any screen size - tablets, phones, desktops, whatever.
Mobile-first design is a strategy where you start designing for the smallest screen first, then work your way up to bigger ones. The mix-up comes from when things became mainstream. Mobile-first became popular around the same time responsive design took off, so people started treating them as the same thing. Most responsive sites these days do use mobile-first thinking because it makes sense.
When you design for a phone's constraints first, you focus on what's most important. Then you can add more features as screen space allows.
But you can absolutely build responsive sites without following mobile-first principles. In fact, I almost always start with desktop and scale down, especially when the website is meant to be used primarily on desktop or tablets.
The undeniable fact is though that when you design for touch, you're already considering users who might struggle with precise mouse movements. So you're already thinking about removing barriers.
Like accessibility, responsive design is about making websites work for real people with different needs and devices.