Of course there was no rules requirement for taking MAs. There are no rules requiring you to take anything at all. You can play with Attributes at 1 and Skills at 0.
But in regards to effectiveness, MAs for higher DV rank very far up. So from a standpoint of effectiveness, taking MAs was pretty good, better probably, than improving skills beyond a certain point or increasing your Str further. You did not have to buy them as Qualities, as you could simply learn them later for Karma and Money. So, no problems there. And 10 Karma for DV+1 seems really good, especially if it's DV+1 for your main combat skill.
MAs in SR5 on the other hand are much more situational, the effects much smaller. So it's a tough question, if you benefit from a MA more than sinking your Karma into Skills, Qualities and such things.