Gotta start some where...Most undergrads dont have jack for knowledge when it comes to research when they first step foot in the lab, despite what they think they know from their classes...and if your under a graduate student, washing their dishes, pouring media, re-culturing bugs (micro), every day saves the graduate student an enormous amount of time that they can use to catch up on papers, work out problems with techniques, grade papers, etc... Those "menial" jobs are much more important than people think, having someone handle them for you is definately not a waste of time for the PI or graduate student.
Every undergrad I took on had to show they could handle washing dishes and maintaining cultures for atleast a semester...They picked up small things here and there - how to pour a gel, the basics of PCR etc..Let them put a couple together towards the end of the semester...then next semester, that becomes their regular job...
Iv definately never had a problem taking any student, pre-med or not, under my wing during grad school if they said the magic words - "I was dishes"...even if they only had time to come inbetween classes to do it...they definately were considered for the job. If they thought they were above washing dishes and what not, no way in hell I am going to trust them with more important tasks. Those that did stick around (2 of the 1-3 I took on every semester over 3 years) actually learned quite a bit, they were easy to work with because they listened to what you said...both of them stayed with me over 2 years and had individual projects by the time I graduated...one stayed on for a masters, the other went off to medical school for an MD/PhD if i remember correctly. They worked their way up..thats the way it should be.