It seems that when HBD was created, the developers thought disk storage was expensive. Either to store too much data, or the impact on the computers to retrieve the data, or both.
It seems they made several choices that probably don't make a lot of sense today. Including showing just the Top 5.
Deleting history was another odd call.
In their defense, it's likely they had a plan to address this as HBD worlds moved on to having 10+, 20+, 50+ seasons. But we're not likely going to see any of that.