[casenmgreen]

I may be completely wrong, but I think one direction of evolution in pronunciation is the gradual shift to that which takes less physical effort to pronounce.

"Bedder" is less physical work, less effort, in the mouth than "better".

[froddd]

“Be’er” seems like even less work. For some people

[foldr]

This is a bit of a myth. A glottal stop is a full consonant sound which takes effort to produce. It's not really any 'easier' to produce than an alveolar stop in any objective sense.