Why is Swipebox slow on mobile browsers?

Question

JavaScript

There are gallery scripts for mobile devices, like this one: https://www.mosne.it/playground/swipebox/ , or this one: cornel.bopp-art.com/lightcase . For some reason, they are very slow in mobile browsers (despite the fact that they work fine on a regular laptop). This is clearly visible even if you view the demo galleries on these sites from a mobile phone - a bad reaction to a swipe, the picture remains a couple of seconds after the swipe, lack of responsiveness. Why is this happening? For example, the mobile gallery on VKontakte works fine, the swipe responsiveness is excellent.