@daut I'm happy to say that this has not been my experience. I suspect - but do not know for sure - that this is actually in part a function of institutional cultures, with places that define themselves as 'top X' sorts of departments both (a) hiring people with the sort of personality you're describing and (b) having especially high levels of pressure around various # and $ incentives that encourage people to view collaboration as a transactional thing rather than something intellectually satisfying and maybe even enjoyable. I feel very lucky to be in a department where I can approach pretty much anybody about anything and get a positive response. I attribute this in part to the fact that we're mid-ranked and while of course there is always talk about what we should be doing to improve rankings, there is not a lot of direct pressure to act in a certain way because of it.

BTW, on an only tangentially related topic, this is one of the reasons I think csrankings is harmful; it directly punishes collaboration across institutions or outside your field.