There are actually a lot of companies with more than 100.000 employees... I think it's just natural that there aren't more... you need a very big market for them
Are you talking in absolute terms or in % ? In % of total companies worlwide, companies with more than 100 000 are clear, small minority. Of course you can probably find a hundred of them or more worldwide, it still does not make them "common" versus the hundred of millions of small-sized companies around.