As others said, people are planning ahead that they may some day have an RV that is 50A and don't want to buy a new EMS. I had the 30A for our first coach and sold it to a buddy when we moved to 50A. The only real difference is the 30A is protecting only one hot line while the 50A is protecting two hot lines.
2015 Legacy SR340 360RB
2014 Jeep Wrangler Unlimited Toad
Gigi, Poppy and Sadie Lady...On the road, but not full time!