Why does grammar matter?  Look to Bruno Mars’ “The Lazy Song” to find out.  He sings about wanting to laze about, but then his line “I just wanna lay in bed” shows up.  What’s up with the that?  The meaning of “lay in bed” is to “have sex with someone in bed,” which confuses the rest of his song, especially when he sings about having sex the next day.  Does he mean to be lazy or doesn’t he?  Or does he mean to have lazy sex one day and then some other type the next day?  Mars most likely meant “lie in bed,” to lounge about in bed.  Of course, perhaps he has the last laugh: it is a lazy song, including in one example of grammar.