Not OP, but I don't think the point is 3G vs 4G. I think (and hold the same ideal myself) that requirements should be kept as low as feasible. HTML gMail is there, it works, it's unlikely its maintenance would break the bank for Google - so why kill it?
We will be pushed to 4G sooner or later, but lower requirements helps at any major events with lots of traffic on cell towers, or a slow, spotty, over-subscribed wifi connection at an airport or hotel. It helps when your main device breaks, but you don't want one app with high memory requirements to kill everything else on your (old) backup.
Here’s my guess: nobody’s actually using the HTML gmail anymore because device and network capability has improved tenfold or more globally in the last decade or so. The amount of people who moved from feature phones to smartphones is basically everyone.
Slow and spotty connections are a nostalgic memory for most people, and even if they’re not, Google provides low bandwidth alternatives via their app and third party mail clients.
It’s fine that this service doesn’t cost much money to run but if nobody’s using it there’s no point.
We will be pushed to 4G sooner or later, but lower requirements helps at any major events with lots of traffic on cell towers, or a slow, spotty, over-subscribed wifi connection at an airport or hotel. It helps when your main device breaks, but you don't want one app with high memory requirements to kill everything else on your (old) backup.