The Randomness wrote...
I'm going to be using fighting games as a huge reference.
It's a difficult argument. The developers want to make money so they put in some new feature for the casual/new people.
For example, Capcom's VS series, X-Men vs Street Fighter, Marvel Superheroes vs Street Fighter and MVC1 had six buttons, LP/LK/MP/MK/HP/HK. Along with specific inputs for the tagging and cross counters. Supers were simplified to QCF+PP as for the games were fast paced.
Then came MVC2, where it was LP/LK/HP/HK buttons and 2 assists, making it easier to tag in and do hypers. Of course, the game isn't easy to master and even with less buttons, it was still a pain for new people.
So TVC takes the route of 3 attack buttons and one assist button. Appealing to a larger crowd and anyone intimidated. Also giving a chance to give players even easier access to combos and no longer needing to be worried about whether it was a punch or a kick.
MVC3 even added a launcher button, meanwhile in the other VS games, you had to get a specific input to launch opponents, such as down+HP or s.HK, in TVC one needed to hold back down+H to launch an opponent. Then UMVC3 comes in and adds an "auto jump" feature when you launch an enemy into the air. But seasoned players and people who know the gist of it know it has disadvantages, especially with timing the attacks. Since it can be turned off, I expect that new people would get used to jumping after launching and learn when to do it, instead of relying on holding down the button, which is bad news anyway.
Of course, the level of execution is vital and one cannot just mash buttons. Easy mode is just there to show you what is possible, meanwhile Normal gives you the freedom to create your own combos. Besides, Easy mode always cheaps out on the button and gives you unintended consequences such as activating a hyper by accident.
Street Fighter IV added shortcuts to special moves, so instead of the SRK motion for Shoryukens; down forward, down forward+P does the job too.
These features are all meant to appeal to the casual/new people, so they can get more sales and get new fans into the franchise.
HOWEVER, keep in mind that back then the technology in games was limited, Megaman on NES being the size of 1 Megabit for example. Games nowadays have Gigabytes for memory.
Along with the fact that games are much more expensive to make nowadays, so going for big sales is pretty vital overall.