When Texas Instruments exited, it's likely neither Google nor anyone else had the proper legal agreements in place to force the release or licensing of the appropriate code/patents to ensure continued updates. After this rather large debacle which affected numerous manufacturers in the mobile industry, I'd wager that's now part of all of them.
Don't forget that even without an exit, sometimes OEMs don't update drivers, leaving manufacturers to drop support far earlier than they should in the lifespan of a product. Case in point, the 2008 Apple Macbook. It only had 32-bit graphics drivers. So, that meant it couldn't run the 64-bit-only OS X Mountain Lion released just 4 years later in 2012. I found this all out firsthand supporting my girlfriend's problematic 2008 Macbook (which also had notoriously bad connections to the LCD panel).
Don't forget that even without an exit, sometimes OEMs don't update drivers, leaving manufacturers to drop support far earlier than they should in the lifespan of a product. Case in point, the 2008 Apple Macbook. It only had 32-bit graphics drivers. So, that meant it couldn't run the 64-bit-only OS X Mountain Lion released just 4 years later in 2012. I found this all out firsthand supporting my girlfriend's problematic 2008 Macbook (which also had notoriously bad connections to the LCD panel).