I find root essential if you use a custom rom. I usually buy cheap phones (like Poco/Xiaomi) and install a lineageOS build. Without magisk/kernelsu there are a lot of apps that are not going to work (like netflix, Google pay, bank apps, et…).
Nowadays most developers consider that you are a terrorist for having a non-oficial ROM and for me using the super bloated MIUI rom is not an option. If you have a good base os like pixelos, samsung’s os or similar maybe you don’t need it.
Also being able to fully block advertisement is a great plus of having root. I now that there are methods that does not require root but adaway, in my opinion, is the best.
Imho NAPSTER. Crazy days of sharing mp3’s files.