"There's no reason" being very different than "we can now do the thing easier". There are still tons of reasons for software to be slow, the biggest of which is priorities.

If you want your software to be fast, stop writing it in Python and TypeScript and instead write it in Go, Rust, C++ or C. But nobody's going to do that, because humans are emotional creatures who get attached to things (like programming languages). Or if you want your software to be fast, stop spending your time and money (tokens) on features, and start spending it on profiling log replays to find a bottleneck causing a 50ms delay for the 95th percentile. But nobody's going to do that either, because how slow is too slow? Answer: when it's slow enough to scare the shareholders or annoy the developer on their high-powered laptop.

If you want faster/more efficient software, force it to run on a 100MHz CPU with 512KB RAM and a 56k modem. You'll definitely prioritize speed then.