Everybody's generator needs are different. A generator needs to maintain basic living services of heat/cooling, sanitation, water, and lighting. Your 5.5k unit would run most well pumps, but if someone also has a pumped septic system, will it run both the well and septic pump at the same time? It obviously would not run a well pump and 4600w water heater at the same time.
In the SE where they get whacked with 90% humidity and days without power, lack of AC can be life threatening. In the West, if you have alternative (wood/NG) heat, you only need a generator and fuel maybe 4 hours a day, and that's only a convenience. 19th century tech kept houses livable with no electricity at all.
My personal opinion is that generator buyers are like pickup buyers. Some people need a heavy duty rig that's going to carry a load, others get by fine with a Honda Civic. Everybody needs to evaluate their physical plant. I know a dairy farmer with a 200kw 3-phase generator, and he still has to load manage and keep a 5000 gallon diesel tank mostly full. He even has a backup backup generator. He's milking over 1000 cows, and can't afford to go down.
Not sure how I lost you, But, I was not asking about anyone else's needs.
For the record: No, I don't have a well pump.
Yes, my 5500 watt generator runs my septic system, my sump pumps, and all my other general needs.
During a power outage, the least of your concerns should be powering a septic system that would otherwise have to fend for it's self anyway, if the power was out. The way my system is built, the discharge sump probably holds 500 gallons, and then has a gravity overflow if things got really bad. So, if I need the power to run a window A/C, because it was oppressively hot, the load from the septic system, is easy to shed.
As I said though, my generator runs my whole house to suit me. Sorry, that it seems most generators can't perform at that level. But, mine does. And, it has done the job for days at a time when I needed it too. So, I don't wish to debate that.
I believe these standby units are often oversized, to meet unrealistic demand calculations, and high sales commissions. However, I also do realize that some people actually need a 20k unit. And, I also realize that I don't.