Why isn’t it common to swipe between top-level views when we use a bottom navigation?

It’s a common pattern on Android that if you have a tabs, you can swipe between top-level views. Google introduced the bottom navigation a while ago, which we already know from iOS. How come it isn’t common that a swipe lets me switch between top-level views when a bottom navigation is used?

For example:

  • Twitter and Facebook on Android use tabs. I can switch between top-level views by swiping.
  • Twitter and Facebook on iOS use a bottom navigation. I can’t switch between top-level views by swiping.
  • Google+ on Android and iOS use a bottom navigation. I can’t switch between top-level views by swiping.

For this question, let's ignore two obvious things, since they're not always present:

  1. that top-level views can contain elements like carousels.
  2. that an app with a bottom navigation can also have tabs.

I can imagine it evolved this way on Android because tabs are more difficult to reach than a bottom navigation. To solve this, we let the user swipe horizontal and accept any usability issues if the top-level view contains any horizontal scroll elements. But this doesn't explain why we can switch top-level views right now.

Another argument for iOS could be that there is already a horizontal swipe gesture to make you go back. This makes it harder for a user to differentiate between 'I want to go back' and 'I want to go that way'. I believe most Android devices still have a hardware button to solve this issue. But that would still leave the behavior on Android into the open