Thinking about all the new technologies and techniques that are available to archaeologists now compared to even 50 years ago, it occurred to me that there might be considerable benefit to leaving parts of a site untouched so that future archaeologists can use what you discover, plus new T&T to discover even more. This is the flip side of contaminating samples and disturbing sites, in a way, but it's as much an extension of the "dig, think, then think some more before digging" approach.
Against that I can see how "publish or perish" and similar pressures create incentives to grab as much as possible as quickly as possible. Not everyone can afford the time and money to focus years on the first thing they find on a site.
Do archaeologists deliberately leave things untouched for later?