Trim string from the end of a string in .NET - why is this missing?

I need this all the time and am constantly frustrated that the Trim(), TrimStart() and TrimEnd() functions don't take strings as inputs. You call EndsWith() on a string, and find out if it ends with another string, but then if you want to remove it from the end, you have to do substring hacks to do it (or call Remove() and pray it is the only instance...)

Why is this basic function is missing in .NET? And second, any recommendations for a simple way to implement this (preferably not the regular expression route...)

EDIT - wrapped up into a handy extension method:

public static string TrimEnd(this string source, string value)
{
    if (!source.EndsWith(value))
        return source;

    return source.Remove(source.LastIndexOf(value));
}

so you can just do s = s.TrimEnd("DEF");

TrimEnd() (and the other trim methods) accept characters to be trimmed, but not strings. If you really want a version that can trim whole strings then you could create an extension method. For example...

public static string TrimEnd(this string input, string suffixToRemove, StringComparison comparisonType = StringComparison.CurrentCulture)
{
    if (suffixToRemove != null && input.EndsWith(suffixToRemove, comparisonType)) 
    {
        return input.Substring(0, input.Length - suffixToRemove.Length);
    }

    return input;
}

This can then be called just like the built in methods.