Being comfortable alone protects you from choosing company purely to escape yourself.

If your own company is intolerable, you will accept nearly any alternative to it, and that acceptance sets a low bar for who gets into your life. The relationships chosen from that position tend to be about escape rather than about the person, and they are hard to leave for the same reason.

Building comfort with solitude is therefore practical rather than merely pleasant. Spend time alone often enough that it stops feeling like a threat. What you gain is the ability to be selective, because you are no longer choosing between company and something unbearable.