You often save time by doing it your self. Mayby not on the one specific task, but in the long run. Because if you ask for, or accept an offer for help, it's expected to return the favor at some point. So the time saved on one task, now has to be used at some other time on some unkown task (that might take even more time than you saved in the first place).
Also take into account, that it often involves socializing around the event, which is now doubled.
And as an introvert, I value my alone time like others value money. I constantly evaluate how to use less on things I don't want or need.