When working as a class tutor, I quite often receive apologies from students for not solving all of the assigned exercises, not knowing how to solve a problem, being absent from the class, etc. This is not particularly surprising - the workload at my university is quite heavy, there is a lot of potential distractions, and people in the UK have a reputation for apologising more than is strictly necessary. I normally don't pay too much attention to this, beyond the factual information that is being conveyed (e.g. a specific exercise caused trouble to several students and so we should discuss it in detail during class), and I try to respond with something polite and reassuring (such as "No worries, this is a difficult problem sheet.").
However, in some cases the students seem to be genuinely quite apologetic, and seem to believe that (what they perceive as) their poor performance somehow troubles me. This makes me feel somewhat odd, because I really don't mind. They're all adults, it's their prerogative to decide how much to focus on each course. The way I see it, my job is to provide them with the opportunities to learn (have their homework checked, discuss problems in class, etc.) and if they don't take me up on it it's actually better for me - fewer submitted problems means less grading, fewer people at class means more relaxed atmosphere, and so on. At a stretch, I could imagine feeling bad if I was the lecturer and felt students' poor performance reflects badly on me somehow, but I'm just a tutor - my job is to grade students' solutions and discuss the problems during class, nothing more.
Would it be a bad idea to explain this to the students? I worry that being too honest about this might be perceived as demotivating or unprofessional. However, I also don't want my students to feel guilty, or to feel like they need to explain themselves to me.