Everyone I know with an iPad doesn't care about tabs in Safari. They just let Safari slowly fill up with tabs, since many links you click on automatically opens the website in a new tab. They never manually switch tabs, they just open a new website in the tab they're in.
As long as a website or app loads up fast, it doesn't matter if it loads from scratch, or was stored in RAM. Except in the very specific iPad usage scenario where: you switch back and forth between apps or website tabs AND the app doesn't support auto save/auto resume or you were filling out a form in a website.
Sure, there are a few users who could use extra RAM. But these users would probably be better served with a laptop, but if they really want to use an iPad, then Apple does gives the option of the iPad Air 2 with 2GB of RAM.
I completely understand why Apple gave 2GB RAM to only one iPad model. The average user doesn't care about RAM would be fine with the $249 - $400 iPads, and the few who do care about RAM have an option to have extra RAM with the $500 iPad.