They can optimise the application: Safari; however, they cannot optimise webpqges for example:
iPad, by default(no apps running)150mb RAM
Then launch Safari and open MR - 100 left
Open more tabs - let's say evey tab is 50mb then you open 3 tabs then the RAM will go to 0 in which the iPad crashes. So Apple flushes one of the tabs to spare RAM. Unless Apple uses Virtual Memory then this will keep happening.
If they optimize Safari, you can have more than your heart desires in open pages. It will be a lot like their multitasking, saved states for most applications.
Save the current state of a webpage, condense it down, then when triggered expand it to the full version. Apple isn't going to release an update just to optimize Safari, they will group it with a bigger update.