I’ve spent two entire days of my life crawling up the seashore measuring the height and diameter of limpets. The conclusion? Limpets get taller and narrower the further away from the sea you go. Why? We don’t know, but they must get stressed through dehydration so having a smaller circumference of the shell must help reduce water loss. They must also be battered by waves so being squat and flat to the rock must help them avoid being washed off by the waves. There must also be an issue with having a strong enough foot to hold on without becoming too tall. They also choose areas where they are less likely to be washed off by fierce currents and where there is shelter from fierce sunshine and dehydration.
Evolution by natural selection. It’s a beautiful and wonderful thing.