Most developers already have a build system to concatenate and minify javascript and css files, plugging in the html minifier is straight-forward and doesn't add any additional complexity really. And since the minification is done at build time on a build machine (not request time on a production server), there is no impact on server side load.
If you were doing templating and dumping in data as I assume most server rendered pages are, it'd probably reduce server side load as you have fewer characters per template
