To be fair it's not wages that are benefited specifically here, it's business expenses in general. If anything, wages are treated worse than other expenses (eg. buying a printer), because they're subject to payroll taxes. As for why expenses are deductible in the first place, that's done for a good reason as well. If you don't do that, you end up taxing x% for each step in the value chain, which would give huge tax benefits to conglomerates (which own the entire value chain) compared to small businesses.