That one really depends on what you do....a lot of the jobs don't require anything beyond passing a drug test. I had to pass one to work at the Post Office, but that was the extent of it.
Background checks become a factor if you have a job where you have access to something that in theory would give you an opportunity to commit fraud, theft, or other crimes. I work with financial records so I had to complete a background check although it was not all that extensive since I don't really have the capability to access any property or money. I only record transactions, monitor the budget, and similar tasks.. The HR person at my job has the most extensive background check of anyone there, because she has access to everyone's personal information, banking information, etc. The supply clerks where I work also have to do a fairly rigorous background check.
Some it also has to do with the particular agency....anyone who works for the IRS in any capacity has to have a totally clean tax record and has to agree to permit them to check their last few years of returns.