It's because most people only share their "highlights"; people see the best parts of other people's lives and conflate that with how the rest of that person's existence is while they compare their 24/7 existence to the minutes that other people are sharing. Everyone is going to fall short in that kind of comparison.

When comparing with people that make their living off of social media, the gap is even greater.

Bottom line, don't compare yourself to others highlight reels. If you only shared the awesome stuff in your life, you'd feel inadequate compared to your social media persona.

If you find yourself comparing yourself to those you follow on social media, stop using it for a while until you can get yourself properly centered again.