This isn't a deliberate behavior, it's something Chrome can't control.

When iOS closes an app in the background (which can happen even if it's still shown in your Recent Apps), it actually clears most of what Chrome had in the local cache. So when you re-open Chrome and it briefly shows an image of your previous tabs, Chrome doesn't actually have the pages loaded anymore. What you see is basically a saved image of what was on the tab rather than content you could actually scroll.

Chrome also cannot preserve tabs for offline use because iOS policies dictate non-Safari browsers must use UIWebView, which doesn't have many caching permissions.