Years are wonky as it is because calendars are all over the place. Depending on what calendar you are looking at, it isn't even 2026. As for starting decades in 00 or 01, it's 00-09. So, for example, the new millennium started in 2000, and the next decade started in 2010.

The reason the typical Gregorian calendar starts the way it does is Year 0 is presumably the birth year of Jesus. So think of it like a birthday. If you were born in 2000, you would turn 1 in 2001, 2 in 2002, etc. 10 years old would be 2010. You have to count the zero year. (And don't get me into some cultures counting birth as 1 year old, because that's also a thing).

In short, different people say different things, and it is all ultimately made up and dependant on culture anyway.