Well from our point of view we already have beautifully researched data from Victoria for 1835. Which we do not have for 1821. If we were to start from 1821 say then we would need to have some time assigned over to this research task. I know you are going to say what about Betas, but Betas are volunteers you can rely on them to do things for you but nothing specific. So we would need to budget in house time on this task to make sure we got the research done. Thus starting from 1835 frees time up for game features, events and things like this.
And conveniently leaves scope for an XP too, eh?