Abstraction is a powerful concept in software development.  Abstracting away certain parts of an application can heavily reduce develop time and make for a maintainable solution.  One shining example of this is the multitude of Object-Relational Mappers on the market, which abstract away a large amount of details about database interaction.  However, as with most things in life, abstraction's highest value is realized when used in moderation.  

While picking up ASP.NET MVC, I've started to realize the significant abstraction that asp.net server controls provide.  ASP.NET MVC doesn't have the parallel (at this point) to the server controls of web forms.  There are html helpers, but those are a very minor abstraction in comparison.  

Whether using web forms or ASP.NET MVC, one could argue that there are always abstractions that don't pull their weight.  For example, it's not unheard of for developers to use label controls for every message they put on a page.  The label abstraction doesn't provide anything that an html span tag wouldn't.  As another example, html helpers in ASP.NET MVC don't always provide much bang for the buck.  In some cases, it's harder to learn the syntax of the html helper than to simply write the html itself.  Learning how to write the html always applies to web development, the helpers only apply to ASP.NET MVC.

Abstractions can make us lose sight of how something actually works.  I will certainly admit that asp.net server controls have prevented me from learning the inner workings of some html tags over the years.  At the same time, they have sped up my development in many cases.  Whether you use abstractions or not, you should first understand what each is doing under the covers.  This allows you to determine if it is adding value or just tacking on an extra maintenance burden.