One important reason they do not use it is the fluctuations of bitcoin prices
Most companies tend to avoid fluctuations. Companies will sell most of their
BTC holding if price were to drop significantly
If bitcoin has been used by many company I am sure the price will go to the moon in next year and everybody will start to invest in bitcoin for sure
All big companies are aware of Bitcoin and will use it as it will fit them.
Most companies do aware of it but the fact is that
BTC is not actually usefull in most of the companies sale as most people still dont have any knowledge yet of
BTC . This will hinder their sale if they were to only accept
BTC, that is why most companies that accept
BTC accept FIAT as well, this makes
BTC not usefull as things could be purchase with FIAT rather than
BTC.
Also that Microsoft do accept
BTC for some sale but it has yet make any significant effect so it is not a guarantee that if a big company was to accept
BTC then it will make a significant effect