Most likely, because it isn't really necessary.
My nineteen year old Kubota has never seen a drop of synthetic or even synthetic blend oil and still starts and runs like the day I bought it. Regular PM is more important than using beyond what type of oil the manufacturer recommends.
I read a lot about people switching to this or that oil. What was it that prompted the switch. Weren't you satisfied with what you were using right along?
I Have used synthetic oil in diesels long before they were even had a diesel rating on the label , ....at the time my company owened over 40 pieces of heavy equipment , the reason I switch was cold weather starting , before I switched with temperatures 32 and below we would spend nearly 1/2 day get all the equipment started , same thing on job site after sitting over night bottom line useing synthetic they started much easier saving me time and money , you are absolutely right about dino oils as long as you keep up with maintenance PMs you will be just fine unless you need your equipment in subzero weather and the oil is so thick it won't start is hard to start , during these time when your oil doesn't flow as it should until it warms up is when damage to your engine occurs ....just saying