Why have they bundled an RTOS with the package ?
It seems to be a 'standard' Keil has the RTX bundled.

Why do you bundle?, well if 98% of the buyers request cruise control on a given vehicle, why keep it an option. After that happens, all other vehicles will eventually make it standard too.

The usual consensus here used to be that RTOS is not required for 8051 apps.
My guess: many buyers of '51 packages are PC programmers that believe they can do the '51, and with that background would not dream of buying a package W/O a RTOS. Then they (hopefully) learn what it is all about and throw away the RTOS, but had it not been there the initial purchase would have been another brand.

Erik