No, they should not and will not.
Streaming may be convenient for those who don't care, but artists make micro-pennies per stream. It takes away from download or physical sales massively, and only the top 2% of artists can actually generate a resonable earnings stream.
When record labels were in a financial talespin as CD sales plunged, they cut a deal with Spotify that basically gave spotify their catalogs for a very large up front payment and a pitiable per stream royalty rate. This was a one time windfall that gave industry suits and lawyers another fat year end bonus and screwed their artists.
Lower end to mid level artists get royalty cheques from Spotify that range from a few dollars to maybe $30-$50. Even bigger name artists have a hard time getting a royalty cheque in the high 00's to low 000's.
I hope that Bandcamp remains an outlet for artists to be able to sell at a fair price and earn a sustainable living wage. Going the sttreaming route defeats the whole purpose of Bandcamp as being for and by artists.