Why do we need thinner ENGINE OILS?

Professional Maintenance Products I Recommend Engine Oil Flush PRO - https://amzn.to/45egARf Engine Oil I recommend - Liqui Moly 5W30 (Made in Germany) - https://amzn.to/46htcs6 Wear Additive I recommend - Ceratec - https://amzn.to/3Q6uYqF Gasoline System Cleaner PRO - https://amzn.to/3tjXcVT Diesel System Cleaner PRO - https://amzn.to/3rCYUkK Diesel DPF Protector Additive - https://amzn.to/3RGJeaI Chapters: 0:00 - Intro 0:40 - 5w30 01:07 - 0w16 02:24 - too thick 03:43 - my shop 04:05 - so many thin oils 08:20 - Extro