I can't really speak nationwide or beyond, but at least here in Memphis, mostly...yes, its the elderly...though every now and then you also get (at least for me, I work the 4-12 shift) those overnighters who work graveyard and sleep during the day...and they come in all ages...over time, you start to get to know 'em...most of 'em are pretty understanding...if you don't catch 'em in the act, there's not much you can do...but some of 'em are adamant that you do nothing but sit at corner X and Y and wait...and wait...and wait...because at XX:XX, the offender will roll through, and you should be there.
Sigh.