It is more useful to turn the lights off automatically when leave the room to save electricity.
In 2018 there are many Z-Wave and Zigbee devices out there that can be put together to make an ad hoc alarm system quickly (less than 30 minutes.)
Many business and homeowners have areas they'd like to keep an eye and that kind of stuff is useful not because it fits a generic need but because somebody can use them as tools to satisfy specific needs.
Wider than that, using computers to control hardware has been a big thing since the SAGE anti-aircraft control system in the 1950s. Even if the "internet of things" in 90% bunk there are big opportunities ahead.
In the case of the car, computer integration reduced some forms of automobile pollution by 99% and has improved safety. I rolled a 7 year old economy car and found the onboard computer activated a pyrotechnic device that pulled my seatbelt tight so I found myself upside down but entirely unhurt. The airbag computer told the dealer that it wanted to be replaced but it went on to perform flawlessly when the car was involved in another crash 7 months later.
There are all manner of places where electronics can go and work wonders even if people aren't aware of it.