1 to used instead of whole infinitive
We can use to instead of the whole infinitive of a repeated verb (and following words), if the meaning is clear.
Are you and Gillian getting married? ~ We hope to.
Let's go for a walk. ~I don't want to.
I don't dance much now, but I used to a lot.
Sorry I shouted at you. I didn't mean to.
Somebody ought to clean up the bathroom. ~ I'll ask John to.
Be and have (used for possession) are not usually dropped.
There are more flowers than there used to be. (NOT ...
than there used to.)
She hasn't been promoted yet, but she ought to be. (NOT ...
but she ought to.)
2 ellipsis of whole infinitive
In some cases the whole infinitive can be left out. This happens after nouns
He'll never leave home; he hasn't got the courage (to).
You can't force him to leave home if he's not ready (to).
It also happens after verbs which can stand alone without a following
Can you start the car?~ I'll try (to).
3 (would) like, want etc
We cannot usually leave out to after would like/ love/ hate/ prefer, want and choose.
Are you interested in going to University?~ I'd like to. (NOT ...
My parents encouraged me to study art, but I didn't want to. (NOT ...
I didn't want.)
However, to is often dropped after want, and almost always after like, when
these are used after certain conjunctions - for instance when, if, what, as.
Come when you want (to).
I'll do what I like. Stay as long as you like.
I hope you find this convincing.