As a good practice you should install SQL server and its binaries on drives other than system drive. But even if you choose to install all features on drive other than OS some files by default will be installed in Bin folder on C drive. Its default and you cannot change it.

Where are SQL binaries installed?

If you're extremely tight on space before installing SQL Server, you will also find that the root binaries installation directory will be, by default, C:\Program Files\Microsoft SQL Server\. When you're using the SQL Server Setup user interface, there is no option to change this.

What are SQL binaries?

In SQL, binary data types are used to store any kind of binary data like images, word files, text files, etc. in the table. In binary data types, we have an option like allowing users to store fixed-length or variable length of bytes based on requirements.