well, it does matter a lot if like some people here, you're a software developper planning on developping on ios or android.
if ios is 10% "market share", it means android is 90%, so you better be learning the subtilities of android sdk and forget about improving your objective c skills. if it's 90% share, it means you can safely tell your customers to start building an ios version of their app first, then maybe later see if they want to invest on an android version.
and finally if it's 50/50, and stays like that for a couple of years, then you should probably invest in some cross-platform development environments.
Market share is often not the best metric to base those decisions on, especially considering iOS has historically generated more revenue for developers than Android, despite market share.
It's also pretty common for companies to sink money into developing native apps for either platform only to find that they get few users and ultimately generate little to no revenue. It totally varies depending on the nature of the product or service, but I've rarely encountered situations where market share was a primary indicator of what platforms a product or service needed to support.
Plus, not everyone of us is out to make millions or build the next Facebook/Apple/Google/Microsoft/Adobe etc. If I can develop an awesome app (or apps) for iOS (and enjoy doing so) why can't I just make a good living doing that? Or even build a small company over it? It sure is heck easier to test on iOS devices than throw it out to the android world, hoping it will be good on whatever device the user chose. It is what it is. I'll take less market share over trying to appease the entire world if it's easier (or even feasible) for me to do so.
Anecdote:
I guess that is why I was so excited to see Sour Cream and Onion Doritos back on the market (only for a short time, dammit). These were my favorite Doritos flavor when I was a child. I bought several bags and now they are gone again. This is what going only for highest profit margins and market share does. This is why we lose our fun sci-fi shows to freakin' wrestling. And, why I can't find David's(TM) nacho cheese flavored sunflower seeds at the store. Grrr...
I think it's more about people wanting to know they're on the winning side.
They purchase an Xbox and then spend the rest of their time convincing PS3 users they made a mistake. Android vs iPhone. Coke vs Pepsi. Mercedes vs BMW. etc etc etc etc.
and finally if it's 50/50, and stays like that for a couple of years, then you should probably invest in some cross-platform development environments.
it's not just marketing, believe me.