Software gets used for mission critical things all the time, with the same level of assuredness. What you are complaining about is that people making apps to show you the right advertisement or a website to watch pictures of cats sometimes is buggy and gets deployed without proper tests.
Meanwhile almost every medical device under the sun today has software, nuclear powerplants run on software, space missions use software, airplanes drive themselves and land through software, etc.
It may be perceived that showing the right advertisements or showing pictures of cats isn't mission critical, and even just a toy. However, when massive amounts of personal information is being collected and shared by such applications I would say they're pretty important.
Notoriously, the 737 Max bug that killed a bunch of people was a software patch over a serious mechanical design flaw, and Boeing decided it was easier to make the software engineers fix it than redesign the entire plane.
Meanwhile almost every medical device under the sun today has software, nuclear powerplants run on software, space missions use software, airplanes drive themselves and land through software, etc.