@angelaEhen
I was with my dh 14 years before we married had a house and two kids, it was just easier to call him my husband and I think if I called him my boyfriend it would feel a little childish.
Why? 
I think calling your boyfriend (who you aren't married to) your 'husband' is a bit more 'childish' than just saying he's your boyfriend.
@NeedCoffeeNowRightNow
mother in law = 3 words
partner's mother = 2 words
Someone please explain why one of these is more difficult.
This. ^
It's not any more difficult to say partner's mother at ALL, and as a few people have said, it does smack of wanting to be married (if you call them your in-laws when you're not married!)
I agree, it is weird. Being married does change many small things - nothing smug about. If you cannot get up to pop into the registry office for what could be a 10 minute ceremony, don't call yourself married.
Exactly this. And people who call us married folk 'smug-marrieds,' are just projecting, and they are also coming across as insecure and bitter.
@saraclara
"We're off to the in-laws" and then "We're off to my partner's parents" .. which one trips off the tongue better.
They are both just as easy to say. But if you are not married, then why the hell are you calling your partner's parents your IN-LAWS? Because they're not.
If I work for Channel 4 as an assistant scriptwriter, should I say I work for Greggs because it's a bit easier to say.?' 
Daft. And as I say, it definitely smacks of people wanting to be married. (calling your partner's parents your 'in-laws...')
And a few people have said people who are married act like they're superior. Maybe they do feel that, and maybe they don't, but you cannot deny that their relationship is more valid than those who are un-married........ Whether the 'un-marrieds' like it or not.
@TabbyMumz
One phrase that I don't get is when people say "I'm as good as married".....I just think "but your not?! Exactly... they're a bit deluded aren't they?!