They certainly tried, and I personally looked at the MSP430 launchpad as a fun distraction last spring ... and ended up ditching Arduino altogether, seeing as most of my projects didn't need the space. What TI was missing was Arduino's IDE, as hideous as it sounds, but they have it now--in the form of Energia (http://www.energia.nu). Still not as established as Arduino though.
Another big hit was the chips they released initially--the 1st gen "value line" chips were hideously underpowered, like 2KB flash/128 bytes of SRAM, more ATTiny-like in size. The current "v1.5" LaunchPad you buy comes with 3rd-gen value line parts, up to 16KB flash, still not quite arduino but doing a lot better (and with hardware UART).
I hope the Stellaris LaunchPad catches on quicker, it looks like OpenOCD is starting to work with it so I have high hopes a UNIX-based environment can be easily deployed for Stellaris development soon. What I am personally more impressed with is the LaunchPad's BoosterPack form factor ( http://processors.wiki.ti.com/index.php/BYOB )--they have thought of a simple and straightforward way to expand the capabilities, while retaining (in theory) some backwards compatibility with boosterpacks made for the MSP430 for example. Much nicer than Arduino's "shield" layout IMO.