I think there is a link between external truth-telling and external truth-seeking.

Say I make a decision for the reason that it is my best guess at the right thing to do in a given situation, based on the facts I have. Suppose further it is not viewed as the right thing to do for social or political reasons among my peers. (This has happened to me now and then.)

I'd like to be able to defend my decision against vaguely stated, uninformed, logically inconsistent or otherwise irrational objections, by reference to measurable and demonstrable facts. I can only plausibly take this position (not guaranteed of success, as I'm sure we all know), as long as I stick to facts. If at any point I become known as a "liar" I lose the social standing to do so in the future, even when the facts are on my side.

Someone with much better social skills could probably charm their way through dispute situations without having to bother with mere facts.

I can't pick apart my tendency towards truth-telling into its various components and their causes, but maybe my love of the truth is partly fear of the quicksand of uncontrollable social situations. I long for solid ground, and stand there fiercely.