The problem with that is that it makes code like $foo} valid, so
I see what you mean (about making it harder to detect problems with braces), but on the other hand $foo} *is* potentially valid code.
For example, here is the definition that originally prompted me to make the change:
%% Centred math environment, spilling into the margins if needed
\newenvironment{mspill}{%
\vskip\abovedisplayskip\hbox to \textwidth\bgroup\hss%
\hbox\bgroup$\displaystyle
}{%
$\egroup\hss\egroup\vskip\belowdisplayskip\noindent\ignorespacesafterend
}
Robin