I am not sure what you mean. Using sequential returns from every starting year in your database is, if I have understood you correctly, the same as using block

I am not sure what you mean. Using sequential returns from every starting year in your database is, if I have understood you correctly, the same as using block bootstrap (at the limit, sequential returns from every starting year is the same as block bootstraps of lifespan length taken an infinite number of times). You don't look at yearly returns. There are many reasons for not doing this but the basic one is volatility clustering. Yearly returns are mostly independent, but volatility is not...again, that is why you use a block bootstrap (you can vary the length of block but for this kind of analysis more than once decade makes sense).