-because that would require everyone to be on at the same time on a weekend which i don't have time to do and i doubt alot of people will have time to do either. stretching it over a longer of period of time is more practicable and more people would actually complete the duels.
It was rather difficult to arrange certain matchups as they were either inactive, ignorant or just didn't have the same times available. Stretching it out for weeks is rather impractical. There are various tournaments that play all "matches" within days. (Want a recent example? Dota2 over the course of 5 days.) If players don't have the time for it for a mere few hours on the weekend, chances are they won't have time for it in general (not explicitly, though). Whenever possible, Bobbe duelled 5 enemies on one day - that worked really well. The last tournament could have been concluded (in theory) within 2 days instead of multiple months.