I take exception to this. It's not a matter of effort, which your post implies, nor is it a matter of lack or respect or whatever. Some people's brains, like mine, don't discern errors because our brains fix them on the fly. I have typos, misspellings and missing words because of this in everything I write. And somehow I've managed to have three degrees in English, and one in law, having taught more than a 1000 students how to write. Sure, proofreading helps prevent this, but for one line posts, it's not worth calling out.