In those days the money was in hardware which cost a lot, and software was thrown in. It wouldnt make sense for IBM to sell their BASIC to another hardware vendor.
Microsoft was different, they would sell their languages to anyone and they did. Can anyone actually name a competitor in those early days ?
Even Apple didnt sell their own Woz written basic to other 6502 vendors, C= had to buy Microsoft Basic.
SofTech Pascal could have been there, too, if they hadn't priced it way out of the reach of hobbyists.
In many ways, that was Microsoft's real genius - charging just a few dollars per user to the manufacturers. Even the Professional Development System was only low hundreds of dollars rather than thousands. They were the first tech company to use the "make it up on volume" strategy.
Software had always been one big project with a dedicated team to build something one off, like building a hospital. Every customer commissioned their own software.
Microsoft recognized that the future was writing smaller software that was meant to be sold to many, many people for less money each.