WTF ?! - a kludgy OS that was outdated at its launch - it had been preceded by better OS's in Windows NT and OS/2. MS should have been producing a Lite version of NT in 1995, but someone in MS was still in love with DOS and wanted to keep building OSs on its ricketty foundation - as they did with Win95/98/ME for 5 wasted years.
It wasn't Microsoft that kept DOS alive (with the possible exception of ME), it was customers.
The kind of compatibility customers wanted, couldn't be provided without a hybrid like Windows 9x.