They don’t in general, but things that do heavily detailed graphics work (like your compositor or browser) or lots of cryptography work on the CPU can get a bit more out of those newer instructions than many other programs.
Very approximately, things that Gentoo offers prebuilt versions of because compiling them is so resource intensive are often the things that can get the best benefit out of your architecture variant. (Not singling out Gentoo here as an example of “doing it badly” - they do the sensible thing by providing these prebuilt binaries, but in some ways it defeats the purpose of optimised source distributions.)
It’s a Hard Problem™ to solve.





As someone who owns several RISC-V devices the primary thing preventing usable (low end) RISC-V laptops is the GPUs. Most RISC-V silicon has Imagination GPUs, and the current state of the drivers there is “proprietary drivers stuck on an old LTS kernel.”
If someone makes an RVA23 compliant chip with open mainstreamable drivers and a BXS-4-64 GPU (or, better yet, somehow manages to license a GPU from Intel or AMD for it), that’ll be a cash cow.