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
