I tend to think that SCP front corporations exist for the purpose of direct action. If you need a property bought up fast, a small corporation or business taken over, or something taken off the market through a lawsuit, but discreetly, you use a front company.
These companies don't have to be huge; Honestly they could be as small as the cabal of lawyers/virtual board members typically behind the shell companies you might read about in the Panama Papers. I could see them being in the know just as easily as not, as long as they're aggressive about implementing their orders.
I don't really buy into there being, like, a giant 9-to-5 corporation or small local businesses under SCP control. Cover companies are great, but beyond a certain point you don't really *need* an actual plumbing company to put on the side of your mysterious white vans. Plus, a lot of the time, it's easier to just pretend to be police, government, or military.
All of that said, the Foundation is not one monolithic thing to all people or articles. If an article needs a megacorp or small business that's been operating openly for 50 years, I don't mind. This is also the major contention behind SCP-initialed front companies, and why I largely don't care about it. Sure, it doesn't make the slightest bit of sense for a secret organization to announce its presence like that, but there are plenty of stories on this site that rely on a certain amount of surrealism, humor, or genre-awareness (e.g., the excellent Learning The Alphabet and S&C Plastics canons) where it makes perfect sense. It'll ding my suspension of disbelief if the article is trying for realism, but that's a tonal choice for the author.