Others have already answered your question for the most part, but let me address specifically what you said above. It's not a waste of a visa page, as as your passport fills up, they'll (usually) look around for blank spots and use them before overstamping. Since there's no notion of the pages necessarily being chronological, by the time your passport is full, all visa page space gets used so there's really no notion of a page being "wasted" just because they skip over it early on.

Upon my last return to the US, they finally spilled over to the Amendments and Endorsements page for the stamp, so I finally got my passport amended to have extra pages put in. I only have 20 months' validity left, so I'll probably not fill up the new pages by the time I renew