Do people frequently encounter players who are more focused on advancing their character than engaging with the adventure? I've only tangentally encountered that level of metagaming. My BRP games certainly don't have a check-the-skill-box focus, but players are incidentally happy when they get the check.
My answer to this would be "these sorts of incentive structures intentionally marry
walking (
engaging with the adventure or whatever) and
chewing bubble gum (
engaging with advancement scheme particulars) at the same time." If a player is in the headspace of
either/or, they need to rejigger their mental approach.
For instance, in Torchbearer, one significant aspect of play for players is managing the multivariate and integrated (i)
tactical now with (ii) the
layered strategic feedback loops with (iii) the
thematic underpinnings and relation trappings of your character (to struggle with and fight for what you believe and who you care about) with (iv) the
advancement scheme and (v) the
intricate currency gain/spend economy. Each gamestate is very sensitive to adjacent and beyond gamestates in Torchbearer and you have to consistently play well and manage an intricately layered, duress-filled decision-space and maintain the bandwidth necessary to consistently do so. Not having all of the feedback loops lined up and dealing with the complexities of confounding incentives and complex risk profiles is (a) where the skillfullness of the play emerges and (b) where the joy of the play comes from (presuming you dig that sort of "locked into the moment" duress and reward landscape). But this is also the primary reason why a lot of folks wouldn't dig Torchbearer, because it is both demanding in a way they're not familiar and they just don't want that kind of duress at the center of their leisure pursuits.
An easy, unrelated to Torchbearer and TTRPGing, for instance is how someone new to the feedback loops of climbing perceive and frame both (a) their intrasession and cross-session progress and (b) the trendline when they're projecting a route or boulder problem that is at their limit. You're going to fail/fall. A lot. A lot a lot a lot. When you're new (and even when you're not), that falling or the looming prospect of it can be particularly neurologically captivating and foil all of your experience in the moment, your ability to achieve "flow state" to explore and deploy your apex capabilities, and your ability to measure and mentally catalogue your actual gains. Same goes for the human propensity to both
demand overriding and immediate positive feedback and
be negative and record losses/failures way more viscerally than achievements. Those things "capture" you and ultimately
foil everything.
In climbing (kind of like Torchbearer), you have to rejigger your orientation to those things above to improve longterm, to have success when projecting "at-limit" routes/boulder problems, and to enjoy the experience of all of it.
Although I guess I could go back to that 4 person group and see if any of them want to play again 
