Certainly very useful for most lightweight database work. What I love about it is that it's all open standards so any client can connect and work with it, and of course there are no licensing costs. If you need more you just branch out into MySQL or other client/server databases.
But SQLite is ideal for embedded devices, Internet of Things (IoT), application file formats, websites, data analysis, caching from an enterprise RDBMS, server-side use in a data centre, as a data transfer format, replacing ad-hoc disk files, internal or temporary databases, stand-in for an enterprise DB during testing or demos, and experimental SQL language extensions.
It's also a great easy way for learners to get familiar with using databases.
See more at Do You Know Python Has A Built-In Database?
An introduction of Python built-in library — sqlite3