Why do people answer Questions of philosophy?

Good question. 

I never ask because I already know what I wanted to learn.

But I don't answer questions in Philosophy. I probably should.

So why do people answer Questions of philosophy?

 1) One of the very first reasons that people have Ideas-of-Philosophy

     is because they are critically compelled to at a very early stage of

their lives (and which I have stated previously here, saying that this can

be the beginnings of subjective-type-philosophy..).

Obviously such philosophy is closely related to getting-to-know-the-Environment

then and so it can be said that (that) occurs naively and critically and probably

sustainably (with a short or long future similar environment ahead. And I bring

your attention to something young Greta Thunberg said about HOW she learned

to answer her (the) early environmental problem/s, by adapting the (her)

method of classifying particular information as "black or white"...See also the

description/s of another individual's early environment/philosophyl-take-up 

that of Helen Keller).

Personally, the types of questions found interesting are simply too specialized or arcane to yield a reasonable time-benefit ratio for questions asked about them on Yahoo!  Philosophy, based on observation of answers to more basic questions about e.g. what is now to be listed.   E.g., if interested in the distinction among Leibniz, Kant, and Hegel, leading to the later work in the field of hyperreal numbers, re Leibniz' Monads taken as generators of Cartesian objects in algebraic geometry, and then how Hegel deals with the Qualitative (i.e., a combination of two Quanta, such as dx, dy) as generating Cartesian objects, all the preceding with regard to Kant's antinomy between continuity and discreteness (in "Critique of Pure Reason") and Hegel's critique of this supposed antinomy, as applicable to Robinson's work as it moves beyond Bolzano, Weierstrass, and others, in terms of the question Hegel raised in his "Science of Logic" re the distinction, not observed in his time, according to him, among users of the calculus, namely that Quanta become Qualitative insofar as they become ratios describing momenta, e.g. dx, dy.  Thus this line of questing provides some insight into the hyperreal as generated by algebra and topology, in the field of nonstandard analysis, which remains personally challenging, even at simplest levels.   (Cf Alain Robert, "Nonstandard Analysis").

Simply time-efficient to consult the sources listed above for answers to questions such as the one sketched above.  As for understanding what Objective and Subjective truly are, insofar as Hegel advanced the subject, would note the insights in his "Science of Logic" as comparatively indispensable, for a basic foundation for further work, including in some cases even the most basic, accurate, and appropriate usage of the terms "objective" and "subjective."

Table of Contents of the "Science of Logic":  Vol. I, The Objective Logic; Book I, The Doctrine of Being; Book II, The Doctrine of Essence; Vol. II, The Subjective Logic; Book III, The Doctrine of the Notion.

A second reason--for answering questions, even if not asking questions:  some people are helped, some people learn, and even that some people are grateful, glory to God.  This latter is what is personally given and understood to be "gain."  Would note that am generally multi-tasking while keyboarding opinions or answers, so also not a detriment, personally, re wise use of time and energy.  And, as many people have noted, it is both rewarding and interesting to answer even very basic, straightforward questions; one may always learn of new associations.

I plead the Fifth.