It's because "to" is being used as a normal preposition in your examples. Suki gave you a bunch of examples. I provided a succinct but detailed explanation of the grammar a few weeks ago, in a post that proved surprisingly popular:

<a href="https://www.italki.com/discussion/164168">Important grammar point: “to +verb +ing”</a>

Another common instance is be used to, for example

"He's a psychiatric nurse, so he's used to working with difficult patients".

Some verbs + to are also followed by  a gerund. e.g.:

object to

confess to

adapt to

Also some other past participle/adjectives + to, e.g:

be accustomed to

be addicted to

be committed to

be devoted to

be opposed to

As well as some noun + to combinations +, e.g.:

a person's commitment/devotion/addiction/reaction to