Design is all about problem solving. Sometimes, you pick a color palette because you need it to work with colorblind people. Sometimes, you study color theory and learn that certain colors evoke certain moods, so you pick your palette based on that. Sometimes, you want to be rooted in a certain historical period, so you find art and design from that time and mirror the palettes. Sometimes, you're creating or refreshing a brand you want to either 'own' a color like Tiffany or UPS or differentiate from your competition, so you look at the colors of your competitors and pick a color that's in a gap.
And sometimes, you or the client wants something that's simply modern/cutting edge/trendy. For me, Pantone's colors of the year solve that problem. In my somewhat limited experience, I've found that the colors they forecast do end up becoming part of the fashion world and in turn the design world. It's not like they pick avocado green and purses end up being emerald instead. Thus, I find it to be a reliable way of starting a 'modern' color palette.
Will a design using Pantone's color of the year end up looking dated? Eventually, probably yes. Does picking their color solve serious issues of accessibility and branding? No. Will slavishly following color trends put you in the top echelon of design fame? Probably not; that's usually reserved for people who make trends instead of following them. But using Pantone's anointed colors serves a purpose and serves it well.