Maybe the 16e sounds good at $599. But, it might be a bit underpowered, so maybe you should just upgrade to the 15 at $699. Then it is only $100 more to just go for the 16 (or 15 Plus), so might as well right? But maybe you want a bigger screen or twice the storage, which are both another $100. Then for another $100, you can get the nicer materials or the extra camera, etc for the 16 Pro...
This is a marketing strategy you see in a lot of the phone market, and has proven to be successful at pushing customers into the higher-margin devices.