They probably wanted to make people actually try in dojo instead of clearing floor 1 and leaving. Problem is this will just turn people off of the content all together.
Like I said the intention was -maybe- good but the way they did it isn't.
They could instead do something like:
You always get at least 20% of normal points, but you also get a bonus based on your tank. Top 100% gets 20% (base) + 0%, top 99% gets 20% (base) + 1%, and so on all the way to top 1% getting 20% base + 100%. Adjust as necessary but the idea is you would get scaled points based on rank. No one gets zero.
This way you always get something but still are rewarded for actually trying.