I believe basically bitcoin was designed to have huge price levels in future so it was created conceptually as an investment in initial days or as long as it is mine-able. Satoshi must have add this investment feature into bitcoin ecosystem for the reason of gaining popularity over quick time. So, investing into bitcoin must be right choice as it is in investment mode right now.
Most of the users are putting their money in bitcoins only because they feel that it can be an best investment for the future as more investors and more companies will enter into the world of bitcoins in future which will certainly take its price to new heights in coming years and we will definitely witness the same in future.