User blog comment:Ducksoup/Why Wikia Evolves/@comment-24473195-20150619235105/@comment-24473195-20150620101730

"Parser functions are good for smaller templates, if you just want to change wording based on the existence or lack thereof of a simple parameter" Not really, even the smallest template becomes confusing with parser functions (PF). You have 24 curly brackets to solve a "simple" problem, not only that but that template of yours cannot easily be figured at first glance primarily because it doesn't use named arguments to keep it "simple".

The power of lua is in re-usabilitity, not  re-inventing the wheel, (see Converting wikitext templates). For example, I designed a couple of modules that make use of a single lua table, and automatically generate information in more than 30 different pages, this includes infoboxes, html tables with stats, and simple wikitext.

I do agree that documentation is lacking in some instances, but wikiversity and wikibookscover a lot. Wikipedia also has a whole library that takes care of frame:arguments.

Using PF is like using a crutch for the rest of your life. As long as it is there, people will always find an excuse to design bad templates with them.

What is lacking is a robust well documented user created Lua library with commonly used functions  stored in a central repository. This actually reminds me of all-in-one libraries created by fans (non-coders) of a hub-soft named Ptokax.