This may be a silly query but I think it is better to ask rather than make assumptions:
I am automating an application that is built in .Net technology yet loading only Web Add-In does the work.
My query is:
when the app is built using .Net technology, then why there is no need for .Net Add-In?
In which scenarios, .Net add-in is required?
Many Web server controls resemble HTML elements, such as buttons and text boxes. Other controls encompass complex behavior, such as a calendar controls, and controls that manage data connections. http://msdn.microsoft.com/en-us/library/bb386451.aspx
My understanding is that .NET add-in is also for .NET Windows application (client/server). My experience is that we can skip it for .NET web application (maybe without controls from 3rd party such as Infragistics). To be on the safe side, I usually check .NET add-in for .NET web application even it might work without it.