Because it let them do things anonymous and its also most likely that they can use it globally and also fast, controllable by themselves.
If you know a person then only it is good to use bitcoins. Otherwise, you may end up in a scam if you send first to an unknown person. Either you need to use trusted escrow to send money to unknown person and that makes transactions slower. It is the main disadvantage of bitcoin. But very useful to send money to known people with less fee and fast.
Speaking of advantages, bitcoin has again increased in value. It seems that a 20$ increase in bitcoin value has occurred just recently. This is the reason why people are attracted to bitcoin. But we'll as you said less fees are also part of the comforts in using bitçoin. Aside from that it enables us to pay bills at the comfort of our homes which gives us savings from transport fee and time. No wonder people shifted to bitcoin aside from being profitable it offers great convenience to users.
