Do you have any insights as to how those internal frameworks developed?
One would think that with the ease and ubiquity of options these days, the homegrown framework (that is often proprietary to the company D-:) over open standards would be disappearing, but I still encounter it often, even in newer products.
The commenter is welcome to his opinion but I think it's pretty wrong. Google has a few internal frameworks for things but mostly they evolved before the standard library had reasonable standardized equivalents and in cases where the standard has grown to encompass these things there's been orderly migration towards using the standard equivalent where it makes sense. It's a quite well maintained codebase with good sensible standards and review process as well as teams of people whose sole job it is to go through to analyze and migrate whole swathes of the code base for improvement.
One would think that with the ease and ubiquity of options these days, the homegrown framework (that is often proprietary to the company D-:) over open standards would be disappearing, but I still encounter it often, even in newer products.