someone27281 So... "people" huh? And you're not able to point to any instance of this recommendation. Got it.
Android is designed SPECIFICALLY to allow you to replace some of these applications with ones that suit you better, and especially in the case of the SMS application, the one that grapheneOS ships with is just a "bare minimum" placeholder that nobody is telling you to keep using. There are tons of better options, like QUIK.
And for the dialer, one of the biggest reasons to use the one that GrapheneOS ships with is because of its ability to record calls, which requires the dialer to be installed as a system application, so installing any alternative dialer will break call recording. Aside from that, knock yourself out.
Contacts? Genuinely nothing forcing you to keep using the one it ships with, aside from the question of "why bother" changing it? It does the job quite well.