The issue is that people often forget to uninstall these apps almost all the time. Apps like Delta, Southwest etc. are the perfect candidate for this. We require something similar to ephemeral apps that exist only for a limited period and automatically get deleted later. If the OS could provide such a feature by default, it would be a blessing. However, this again contradicts the commercial interests of many companies and services, so Android and iOS will likely never implement it.
My android phone will put apps into "deep sleep" and remove all their permissions if I haven't opened it in a month or so. I just toss travel apps into a folder in my launcher and they are there if I need them but become just a consumer of drive space on their own.
When it comes to airline tickets I've been able to check in to a flight through a web page and then add the boarding pass to my Google Wallet without having to install that airline's app before. I'm pretty sure Apple has had some similar kind of a workflow but I wouldn't know for sure.
Appclips in iOS are a decent shot at that. But require it to be under 15MB, which is really hard to hit, especially if you use RN, but we'll be dumping RN to make this happen as a next step.
>>The issue is that people often forget to uninstall these apps almost all the time
Fundamentally though, iOS will auto-offload the unused apps for you (you won't get any notifications). For all intents and purposes, it is an ephemeral app already.