It seems like they must get some benefit from being secretive.

Well, if you were trying to build a facility to cure cancer, etc, and didn't want to be bothered by hysteria and all that shit, why would you draw attention to yourself? I don't see the point of announcing themselves.

Well, if they just marched into towns across the country and started eating people in broad daylight, there would be widespread panic, and maybe people fighting back, right? That's not a smart plan, especially when humans still have to outnumber them in the hundreds of thousands.

It makes me wonder what their limitations are - plus if everyone learned the borax trick. . . hmmmm, why aren't they trying to corner the market on borax?

Especially if they're not there to eat people. They only seem to be eating them in order to get stuff, not as food or fun. And if Joyce's style of frivolous eating is frowned upon--I'm guessing that you're only really supposed to do it if you're replacing them.

When they first started taking hosts they were eating people for food and fun as well as disguise, though at that point they seemed fairly unfamiliar with the way the human world works. I guess I just don't see their motivation for pretending to be people and making themselves into this big corporate conspiracy, aside from its utility in monitoring and finding specific opponents/victims as with the Winchesters.

I guess I just don't see their motivation for pretending to be people and making themselves into this big corporate conspiracy

But we don't know their goals. So how could we know that being obvious is more in line with them than blending in/being in the shadows? Monsters don't tend to blow their covers, so I don't see why Leviathans should be expected to.

All we do know is that their goals seem to be furthered by corporate shenanigans, and there's no advantage to screaming "Cthulhu!" as they enter the boardroom. Path of least resistance/Occam's razor/all that stuff just suggests to me...go with the flow.

There seems to be such an air of necessity about it though, to the point of the lower-hierarchy Leviathans being threatened with "bibbing" (I assume that involves self-destruction?) if they blow the cover too much. My impression is that we've seen less commitment to secrecy from monsters that are a lot more vulnerable, like the vampires and shapeshifters that organized to grow their ranks in Season 6. And it started before the Leviathans even knew human beings had any weapons that could hurt them.

there's no advantage to screaming "Cthulhu!" as they enter the boardroom.

That sounds like an improvement over the usual meeting.

The Leviathans aren't really working for me as a Big Bad. There are too many of them and the stuff they do seems so random.

"bibbing" (I assume that involves self-destruction?)

Bibbing was what Dick called it when they made the one Leviathan eat himself.