A quality thesis can go a long way, but they feared that often times, the product was less valuable than doing research under a major grant in a faculty member's lab and maybe even getting published with them. As the above poster said, it's about what you learn (though you should also be doing), and at the undergrad stage, it's hard to learn on your own if you have little direction.
I agree with your post Veggie! I just want to clarify for the benefit of the OP and other applicants.
It seems to me that most undergrad roles in research is.. well lack luster. I think this is normal. I spent too many hours with a pipette in hand. On another project, I just ran audio equipment, and on another I coded every minute of a 30 conversation with a 1, 2, 3, or 4. Nothing fancy, but I learned a lot and I had a lot of ideas. I expressed all that, in one way or another, to in personal statements and interviews. My feeling is that they were impressed with what I had learned, even if what I did was really grunt work.
My point is not to be disparaged if you don't get a position where you get a publication and a patent out of it. I think those are rare, and you kind of have to get lucky. The experience is what you make of it. Ask a lot of questions, take opportunities to learn about what everyone (grad students, other undergrads, the head of the lab, your professor, the janitor) does to contribute to the project.
On the other hand, there are experiments where no one will be helpful. My friend once worked in a biolab where no one really talked to him or taught much. He tried, but even the professor was difficult to talk to. That was probably not a good place to get good experience, and to be sure, he left after a month or so.
In short, it's not about finding good research experiences, it's about creating good ones. If you can land a position where you will be an active part of the design team, get your name on publication and a patent, be taught all these lab techniques... do it. Take it and never let go until you graduate! However, if you find yourself doing grunt work, there's still a lot you can learn about the research process that will be valuable to you when you apply.