The problem is that in this scenario someone else (i.e. the sender) is choosing the product/application they want to run on my device in my app. Unlike a web page, where I (hopefully) intend to use it and "pull" the app, this is designing a system where arbitrary apps and interfaces can be pushed to me by others, often not with my best interests in mind.
I don't want my email client to be part of such a system. If I want to follow the advice of "if you do not like the product then move on", then it's not sufficient for me to simply not use this feature in messages I send, this requires that messages I receive don't/can't use this feature.
I don't want my email client to be part of such a system. If I want to follow the advice of "if you do not like the product then move on", then it's not sufficient for me to simply not use this feature in messages I send, this requires that messages I receive don't/can't use this feature.