Power at low RPM equates to more torque. Torque is sheer twisting force. The more you make the harder it is on parts. The I4's don't have much torque down low. Largely due to what I explained already in that you have more cylinders spreading out the power over more crank rotation rather than a couple pushing much harder. This coupled with the timing that Hawk is describing having a hard push then a lax coast to a hard push again makes for an extremely jerky on off power delivery especially down low and tears up chains, and sprockets if you use sup par parts.

As for the manufacturers doing something about it they do. They use higher quality 530 chains that will hold up to it. The reason people use 520 is because they are lighter as stated already. If you don't care so much about the longevity but do about performance, such as a track bike, then it's a great option.

The reasons V twins pull better out of the corners is the torque they make. They have much broader power bands and don't have to be revved to the hilt to get the power out of them. Also I'm sure you'll also notice that generally a V twin will have more displacement in the same class as a comparable I4.