People prefer Bitcoin to altcoins, because bitcoin is more secure. Most people getting involved with some altcoins is to enable them reap and have a taste of how earlier adopters of bitcoin did in its early phase. But most of these Altcoins have failed to prove and meet expectations of those who adopted it from it inception, Altcoins instead of focusing on building a better foundation they focus promises that are impossible to realise. After peiod of time, instead of improvements, some altcoins tend to keep struggling to maintain it value. While Bitcoin long existence has proven to be solid and maintain its value over the years, even when bitcoin falls it's ability to overcome downturns and bounce back makes it a more unique preference over altcoins.