In addition to the great reasons others posted, I'll point out another one: Most airline apps won't even install or run on my device anymore. So, even if I want

In addition to the great reasons others posted, I'll point out another one: Most airline apps won't even install or run on my device anymore. So, even if I wanted to use the airline's app (I don't), their developers have chosen to not support my device, and therefore I cannot even install or run it. If a company is going to make something a requirement like this, they need to also invest in the effort to support everyone's device, and not block people with old, icky phones.