I'll put this into personal context for you. Whenever a plumber or other tradie comes to my property, I have to wonder if I'm going to come out to them by being specific about the "we" in our household. Do I say "my husband" and use he/him pronouns straight away, whilst wondering if they're going to have a problem with our sexuality and feel uncomfortable being in our house?
Similarly, when I check into a hotel with another man and am asked, "do you want a twin room?", will I have to come out when I reply, "no, one bed is fine" and wonder if we'll be silently judged? Or if I'm buying flowers at a florist or ordering two meals at a take-out restaurant, will the staff say something like, "that's a nice treat for the missus" and will I then be bothered to come out to a stranger and correct them? Or will I just let it go?
I'll be the first one to state the problem here is my internal belief system about the world, not the people I encounter every day. I'm not giving them enough credit by wondering if they'll be uncomfortable by my sexuality; in reality, they probably won't care at all.
Yet, when you're a queer person, this is what our heteronormative society has conditioned us to think. From childhood we've had it instilled in us that we won't be liked or accepted by all. We carry that – some more than others – every day. Developing progressive attitudes in Western society do help, but we don't kid ourselves: not everybody is OK With The Gay. We must live with the assumption that we are seen as heterosexual until proven otherwise.
Some straight people have no problem with homosexuality, but don't like overt or "loud" public expressions of it. They don't mind you, but they don't want your gayness "rubbed in their faces" or "shoved down their throats", as the clichés go.
As coming out is something we have to do every day as queer people, I now want to make the argument that we should all present a bit "gayer". If we were all to dress more queerly, talk more queerly, and have queerer mannerisms, maybe we wouldn't have to verbally come out so much? If I presented gayer, could I dissuade people asking me if something's for my girlfriend/wife or wondering if I've made a mistake booking just one king-sized bed?
I am of the belief that being able to hide your LGBTQ status (whether it's for your personal safety, comfort, or another reason) is a contributor to gay shame, it doesn't make our minority status easier to live with. That doesn't mean it's not necessary. Indeed, it's not possible for a lot of queer people – and nor should it be. An LGBTQ person should never have to dull down their outward appearance for the benefit of others, and I hate that we feel we sometimes have to so we can get along unmolested in the world – especially outside of large metropolitan cities.
So where do we go from here? I have one idea. If you're straight, help us LGBTQ people by challenging others when they presume your heterosexuality. If you're a straight guy, for example, and a stranger asks you about your "missus", politely ask why they've already surmised your sexuality. If you're a straight girl and you buy a gift that somebody naturally believes is for "your man", smile and rebuff them with something like this: "how do you know it's not for another woman?!?"
The result should be that others begin to second-guess themselves and will stop making heteronormative conjectures about people they don't know. These small, seemingly inconsequential actions on your part help solidify your LGBTQ ally status, and should – over time – mean we as queer people don't have to come out of the closet so damned frequently.