A Profile layout is the display of member profile. In version 4 this is no longer the same BuddyPress profile. The disadvantage in BuddyPress profiles is that they do not allow page caching. The content on the profile pages is not static, for example the activity tab changes frequently, any content which comes frmo the server dynamically can not be cached by the browser, so a hit has to be made to the server to fetch the page hence such pages will always load slow. Other reasons, firstly a public profile displaying activity can be a privacy issue, secondly we really do not understand how useful it is for a third party user viewing the profile, none of the top sites have similar structure, including the facebook. A public profile should be static, configurable and showcase what the member wants to show.