I brewed for years on my stovetop with a 30 quart pot, and a 10 gallon cooler and it made great beer.
The thing is, lifting all that water and pouring scalding water into vessels got old for me. I first went two tier with one pump, but then found that going single tier with two pumps worked best for me. I never lift water, as it goes directly into the HLT where it is held and heated, and them pumped into the MLT. I never lift hot wort, as it's pumped into the boil kettle, and I never lift cold wort as it's chilled and pumped into the fermenter.
Overkill? Maybe. But I"m a 52 year old 135 pound weakling- without the pumps I would have quit long ago. It's also less work for me, since everything is all set up all the time- no hauling/moving/lifting equipment. The vessels are all decommissioned kegs- they weigh about 30 lbs even empty and there are three of them. The chiller is light, but yet another thing to haul around. In my case, everything always remains on the stand, and the stand has wheels if I want to move it. I also have it set up with all-electric, so I brew indoors in my laundry room. It's so convenient for me- no pulleys, no mess, no lifting.
The other thing to mention is that I"ve been burned quite a number of times by pouring hot liquids, and did injure my back once with all the lifting and transferring.
Of course, I've also been scalding by a loose hose on the single tier also, when it shot off and shot hot water at my chest. So there is always a risk of injury when dealing with hot liquids, electricity, and/or propane. I just feel that it's easier for me with my system and less "work".
