Corporations are legal persons, and income accruing to distinct legal persons is subject to tax. E.g. I get paid by my employer, and then pay tax on that. Then I pay my nanny with post-tax dollars, and she pays tax on that. That's not "double taxation"--just the nature of an income tax.
Imagine that instead of forming a corporation, a bunch of investors nominated Bob to be the legal entity in charge of the whole business. Bob held all the bank accounts, directly employed everyone, and booked all revenue minus his expenses as his income. A series of contractual arrangements required Bob to pay out the profits to the investors. Under that circumstance, there would be no doubt that profits would be taxed when they initially accrued to Bob, then again when he paid the investors.
It should be noted that nothing precludes companies from organizing as something other than a corporation. Partnership income, for example, is only taxed when it is received by a partner.