Boners are a man's best friend, and we love 'em!
Yet, as Anonymous pointed out, they can be annoying, as well, popping up out of nowhere, at the most inopportune times,
As a character in That Awkward Moment stated, "It's a blessing and a curse all at the same time!" and we're forced to deal with them. In our school-day youth we hid them behind books. When we no longer have tomes to hide the bulge, we arrange them as best we can to minimize them being obvious.
As French Patrick points our, it is mating season for many species. Humans, though we can (and do) engage in sex at any time, do not seem to be immune from this time of year. Perhaps it is a surge in Testosterone, as Jean points out, that has our cocks rising up and insistent.
It could also be a complete throwback to our origins. Perhaps we, too, had our season of being in heat.
Whatever the case, we're left to deal with our aching man-berries and rising appendages as best we can.