But mining also requires quite a lot of costs so that it can run well and generate a lot of profit. And maybe some people choose to invest in IEOs/ICOs because they can get a quick profit when the tokensale or crowdsale is complete
Mining without a doubt requires a huge capital and technical knowledge just to start the operation but it is a lot more predictable compared to being a trader or on investor, especially if the coins in which you are thinking in investing are icos or ieos that as we know have a very high chance of failing during their first year of existence.
And even if there is a chance of getting quick profits I do not really think that a lot of investors really believe that anymore since they are very aware of the bad reputation of most icos and ieos.