Apparently you don't understand the (many) differences between a Piano Roll editor (DAW) and a dedicated drum sequencer.
They are, quite simply, very different approaches to sequencing. Some DAW's have built in drum sequencer (cubase and logic come to mind, and I think Studio One just added one recently) but many others don't. And often the ones inside DAWs are very clunky / not nearly as full featured as dedicated drum sequencers like those found in Geist and Tremor.
But if your point is that nobody should need a drum sequencer because we already have a piano roll....well uh...you've missed out on a major part of sequencing rhythm sections, my friend.