My most recent commute arrangement was to carry my things in a large saddlebag (Carradace Camper) strapped to the saddle. I was able to park my bike inside the office, so there was no need for a bag that could be quickly removed from the bike. Previously I had used a pannier bag when I had to lock my bike up outside. But either way I still had a rear rack on the bike. Even if not needed for the daily commute it was still handy to have for other utility trips.