I develop my web applications using only PHP for the view files and I don\'t feel limited in any way, but I hear there\'s a consistent number of developers advocating \"external
Separation of concerns.
This sort of things comes as standard when using a MVC/MTV approach - where the presentation of data is necessarily separated from the display of data, but not if you're using plain ol' PHP.
Using a template engine makes it easy to separate out what's being displayed from how it's being displayed.
I suppose you could argue that this falls under "babysitting bad developers", since a good developer ought to do this anyway, but in my view, a template engine makes it easier for good developers too.