The TL;DR is that every anomaly that your database can experience is one thing that every developer needs to consider for every change they make. This is a huge

The TL;DR is that every anomaly that your database can experience is one thing that every developer needs to consider for every change they make. This is a huge overhead. Most importantly every developer won't correctly consider these anomalies for every change because humans aren't perfect. This means that you will encounter bugs from time to time. So that is the purpose. If you solve this at the database layer you relieve your developers of this burden and reduce bugs. You can argue that the cost is too high (it may be) but there is clearly a benefit to balance it out. Especially if the cost keeps dropping (as it seems to be doing) the balance tips every in favour of stricter consistency models.