WHy do people buy alts before a bull run when btc leads and everything else follows

Do any of you guys ever wonder as to why people buy alts before bull runs instead of just buying BTC? If you look at the last few bull runs BTC always leads the gains and all other coins follow a few months later with all the btc owners selling and taking profits and going for other returns in the smaller alts. Why would anyone risk money in a smaller alt instead of just going with the best asset in history and then buying into the alts once you have made your profits? It's crazy to me. whats everyone's thoughts