For those of us who run in sub freezing temps, tights are super important to keeping your legs and lower bits warm.
When the temperature is around 30-40 degrees I’ll make the transition from shorts to tights. I usually just wear my regular boxer briefs that I wear on a daily basis under my tights, they work very well. If it’s a really short run I’ll wear regular underwear, not a problem for a half hour jog.
A nice thing about tights is that you can usually get away with only 3-4 pairs since they don’t really get sweaty from hour easy runs when it’s 25 degrees out side!