Over extended sites with long loading times?!

I don't have a highly capable computer or internet speed by any means. I mean I have a run of the mill spec laptop and the highest available residential internet package from Comcast, fiber optic.. but I'm by no means a techie.. a nerd sure, but not the most knowledgeable tech guru.. However, I do know sites with a long load time miss out on a hug chunk of business.

Is it something on my end? I should be perfectly within average consumer range as far as specs go. Are their added features making up for their bounce rate, because on average that's a pretty large margin lol Is there something I'm missing? I see a lot of money sites with really heavy loading times, that would otherwise be pretty decent sites.

I'm not a web design guy hence my crowd sourcing any useful information. I mean I know about servers, but surely there's something I'm missing... why would a money site not make sure they can handle the traffic thrown at it?