Max of 59 for suitcases?? is that too big?

I had a question, in the contiki book, it says your suitcase can have a maximum dimension of 29"x20"x10" (HxWxL)= 59" and a max weight of 20kg i was wondering how many people bring a suitcase that big? i have a 29" upright suitcase and for my tour, European Escapade, it's 27 days long and i think the suitcase is enough if anything maybe too small (i pack heavy) do travellers on tour 20 days or longer bring the max allowed or usually pack small and compact??
i don't want to look like the only fool lugging around a huge suitcase