You are looking for a job and there’s a job fair in your area with very interesting companies. Unfortunately it is on Saturday. Should you go?
Let’s say you manage to not break any actual commandments. You walk there, you don’t carry anything, you don’t sign your name and so on. Which in itself is a challenge, because giving and receiving business cards without carrying is … difficult. But let’s say you manange that. Imagine you managed to get an interview at one of the companies. In the interview you mention that you need to take Shabat and the Jewish holidays off. Your interviewer remembers that you met at this job fair on Shabat. How serious are they going to take your request? You can explain the technicalities all you want, I doubt this is a good starting point.