Out of curiosity, if there are no fees, why not? That lets you theoretically diversifying your risk by investing $1,000 in 30 companies rather than say $5,000 in 6 companies.
The zero fees might still be nice if you want e.g. to contribute every paycheck; but an old-fashioned Vanguard mutual fund would be just as good for that, or many brokerages have zero fees for specific classes of ETF. The only advantages that I'd see to Robinhood are (a) no minimums, and (b) pretty UX.