t-string main use case is SQL (for instance, in psycopg¹)

You can write things like that without SQL injection:

  t"INSERT INTO mytable (first_name, last_name) VALUES ({first_name}, {last_name})"

This is a very pleasant feature, very useful

[1] https://www.psycopg.org/psycopg3/docs/basic/tstrings.html