They removed it because making payments in Bitcoin was no longer viable. Who want to pay a transaction fee of $100 for purchasing a Microsoft Office Suite which costs $150? The charges levied by Visa/Master for the same is around $3 per purchase.
It was also according to my friends the transactions for bitcoin is really expensive so that they are much more prefered not to alts coins And I think this is what I do too. 
Topic: Microsoft Removes Bitcoin - page 5. (Read 705 times)
why Microsoft Removes Bitcoin as Payment Option for Microsoft Storew?
One of the reason mentioned was the high cost payment. So if you have a small amount of btc you cannot use/redeem anymore.
But recently Microsoft restores btc payment after the issue of paying is resolved.
The lowest amount of btc is already ensured that it can be redeemed.
Because US government is against cryptocurrencies. As long as Microsoft doesn't want to have problems with officials they won't take any risks. Especially risks like that: Bitcoin as a payment method is only for geeks and it's not worth keeping it just to satisfy them.
They removed it because making payments in Bitcoin was no longer viable. Who want to pay a transaction fee of $100 for purchasing a Microsoft Office Suite which costs $150? The charges levied by Visa/Master for the same is around $3 per purchase.
All these big players, once they start to adopt bitcoin usage alot of other companies will start to follow suit. 
why Microsoft Removes Bitcoin as Payment Option for Microsoft Storew?
I seen this 2 days ago..
https://www.neowin.net/news/microsoft-to-stop-accepting-bitcoin-as-payment-method-due-to-volatility
They said the reason was volatility.. just like Valve inc.
EDIT:
Oh and i recall the story way back when they removed it and added it back a day later saying it was an "accident" too.
why Microsoft Removes Bitcoin as Payment Option for Microsoft Storew?
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