I blame Ed Greenwood. The original FR boxed set specified that FR elves were as tall as humans but more slender, and over time that became incorporated into the core. 4e had elves and eladrin be slightly shorter than humans, and that's been transferred over to core 5e.It's weird how D&D elves have gotten taller over the years. When I was first introduced to D&D as a kid, I didn't like elves being short and I wanted them to be tall like Tolkien elves. However, now I actually like short elves, it makes them more distinct.