1. Good luck finding all places that access some table if you want to change something, especially if table is called users or products.

2. ORM provide abstraction layer. Otherwise every place needs to know all details of tables it accesses. Migration from db to solr for example is much easier with ORM. Ensuring that you call strip_html or other logic in all relevant places is also easier if you have one entry point you can hook into.

3. Strings compose poorly. Building complex queries from set of parameters sucks.

4. Database portability is crucial, even if you will never migrate. It gives you access to far greater mindshare and toolset.