I don't get it, why would people would invest in BTC now? current price is $16K but people still invest in it.
even if it reaches imaginary price of $32K people would get just +100% of what they've risked while you can invest in altcoins and MAYBE get easily 10x-100x on your risked amount...
If you think that 100% is not a good profit then you don't know much about investing and economy in general. If you are going for 100X profit by investing in some shitcoin you are basically gambling with your money, as that's what it is. And if you like to gamble, then better head to casino ,at least you will know immediately whether you win or loose, instead waiting for month or in some cases even years for some shitcoin to "moon". But if you want something more solid, bitcoin is way to go.
Regarding your question why people still buy when price is 16K+, answer is simple: because it will go up more and it is still not too late to join, no matter what someone told you.