That's definitely a reasonable perspective, though it depends on a very particular notion of What Game Rules Are For.
Suppose, for example, that your tabletop RPG character has occasion to play a game of Texas hold 'em. There are two basic ways this could be played out:
Roll some dice to decide who wins, and based on the outcome of that roll, produce a description of your character having played a game of Texas hold 'em.
Pick up a deck of playing cards and play a round of Texas hold 'em, you in the person of your character and the GM in the person of your NPC opponent, making all relevant decisions in character as your respective roles.
We certainly wouldn't say that the second one less constitutes "roleplaying" than the first. Some in-character activities, however, are less amenable to this sort of step-by-step acting out – at least, not without a lot of special equipment – and one of the functions of detailed frameworks of rules, such as the prototypical "combat system", is to furnish a game-mechanical proxy through which this sort of fine-grained IC decision-making can occur.
(Hell, if you were feeling mischievous, you might even argue that a game with a crunchy combat system is more "RP focused" in this sense than one which simply produces produces a description of your character having had a fight, in the sense that it both obliges and enables you to act out the process of actually making all those nitty-gritty IC choices.)
From this perspective, one might easily conclude that the purpose of RPG rules is to furnish such game-mechanical proxies; by extension, when no proxy is needed because sitting at a table poses no obstacle to acting things out in detail, game mechanics need not enter into it.
That's not the only possible perspective on What Game Rules Are For, though. Take me, for example: from my perspective, game rules are toys. They're made of methods and procedures rather than metal and plastic, but they're toys all the same, and I want to mash their faces together like a kid making their action figures make out. Whether or not a game-mechanical proxy is strictly required in order to play out the activity in question just isn't terribly relevant to me, because that's not why I want the rules to be present in the first place.
This being so, if somebody comes to me asking how best to address or model a particular activity in a framework of rules, I'll assume that they likewise have a reason to want such a framework to be present. I've got nothing against freeform RP, but I'm going to do you the courtesy of assuming that you've already considered and discarded that option and aren't just wasting my time!