Buy and hold for a long time is the best source of bitcoin now. For those that buy bitcoin since November last year when bitcoin price was around $600 for just five months has made over 150% return if they sold their bitcoin today.
Yes you are right. Just buy and hold now is very profitable. But not everyone has enough faith and patience to just keep. Some people take risks and lose their coins
Buying and holding bitcoins for the future is the safest way to make profits but the only issue with holding is that it will never help you in growing your coins so people who feels holding as boring will surely take some risk and will invest their coins in trading to grow them faster and also to make regular profits.