I think that one of the main reasons to buy altcoins is to earn on them.
Many people earn money on cryptocurrency. That is why no wonder that they want to spend their cryptocurrency for buying different goods or to vocations and different trips.
Many people use altcoins for investment purposes because it is possible to earn more money on altcoins that on Bitcoin.
When market rise the price of altcoins rise evern more then Bitcoin and such big rise attracts a lot of attention.