How normal is it to have published as an undergraduate?
Throughout every country and every field that I am familiar with, it is fairly unusual to be part of a publication as an undergraduate.

It is also the case, however, that those who did publish are more likely to go on to graduate school, and that it would be unusual to have a class of any significant size with nobody who had published in it.  I don't know the actual statistics, but let's assume only 1 in 10 undergraduates who go on to grad school have published something as an undergraduate, in which case in a class of 20 students, there is a ~88% chance that at least one person would have published. 

Thus, it might well be surprising to the lecturer that nobody had published, even though publishing as an undergraduate is fairly rare.

Note: the numbers that I gave were notional, just in order to illustrate the way likelihood is non-intuitive for a whole class.  As a point of reference on the high extreme, however, consider that 85% of MIT undergraduates participate in on-campus research programs.  A lecturer coming from a high-density research environment like that may well have biased expectations about research frequency.