I work with word, PowerPoint and excel on Mac and on pc basically every day and they are pretty similar. I think Microsoft did a pretty good job making them comparable this time vs the 2011 version being very different than the programs on windows.
It appears your problem is only with outlook on a Mac, what exactly are you missing? You keep saying features or feature sets but nothing specific. Do you have any examples of outlook on Mac being worse than on windows?
Also, you said you just bought this, can you return it wherever you bought it from? May not be possible, but if it's only been a few days it's worth trying to return it if you are truly this unhappy with it.
As for the question of why a lot of corporations use windows, I think the majority of corporations use windows largely for cost reasons. I (read: my job) just dropped $2500 on a new iMac and $2300 on a new MacBook Pro for instance. For most office workers, a word processer and internet browser is all that is required with maybe one or two simple applications. For those uses, it makes sense to buy a $300-$500 pc vs a $1200 base model iMac. Obviously this isn't the case everywhere, but I think that is where a large disparity comes from.