Why ppl still buying bitcoin? There are many things, like someone think that bitcoin is secure, someone think bitcoin is really annonym, someone think that bitcoin easy to use (cause you can use bitcoin everywhere), or something like that...
And about ROI by investing on bitcoin>>dude, do you never ever hear/read thing that called crypto trading? By trading on crypocurrencies you can earn 100% profit only for few month even day (pls note that cryptocurrency not only bitcoin)
How about "why ppl not investing/buying gold/silver?" as I said above, it's because they think bitcoin is safe (if you investing on gold, you have probability to get robbed bigger than investing on bitcoin, why? Because till now (atleast), nobody can't hack bitcoin...