There are other uses for ASM aside from getting more speed. Learning ASM will show you how things work at a low level, which is helpful when you try to understand C pointers and other details. Reading assembly also lets you (try to) understand the programs you don't have the source for - device drivers¹, malware¹, copy-protection, regular third-party applications ...

I spent several years disassembling a game (C&C Red Alert 2), understanding the code, fixing the shitty parts and glitches left in it, and extending it. It was fascinating.

¹These examples are certainly far from trivial, I know, but that is half the fun.