Most Arabic dialects are just that: dialects. They have no grammatical rules, nor a official written form for that matter, and are ultimately used for nothing more than speech.
> They have no grammatical rules
Nonsense! All languages and dialects (not just prestige ones such as MSA or Standard English) have grammatical rules. If a language didn't have grammar, it would be impossible to express the distinction between "the dog bites the man" and "the man bites the dog".
Exactement.
They have lots of grammatical rules! See http://arabic.desert-sky.net/g_tenses.html, for example.
Arabic speakers tend to diss their dialects and dismiss them as 'mere speech', but they're just as rich as any other language.
Yes, but these rules are applied in a spoken form only, not to mention the fact that they are not studied, but are instead learned over time and in no fixed order.
Besides, nobody would write an article in Egyptian Arabic or any other dialect for that matter because it'd simply be a waste of time.
Surely they do follow grammar, albeit the grammar of whatever colloquial Arabic they are speaking, rather than the grammar of Modern Standard Arabic?
In terms of colloquial Arabics, do they have less complex inflexional systems compared to MSA (in the same way that Italian and Spanish do compared with Latin)?