Motivation for All Upgrades since .NET 4.5.2

 Targeting .NET 4.5.2 was a huge milestone in stability.  It was the "final" version for most projects in the past 8 years, I'd wager.

Then in 2017-18, everyone had to jump ship.

https://docs.microsoft.com/en-us/dotnet/framework/network-programming/tls

also see:

https://stackoverflow.com/questions/28286086/default-securityprotocol-in-net-4-5

And this:

https://medium.com/@kyle.gagnet/your-net-code-could-stop-working-in-june-afb35fbf29ca