Because nobody uses them. Running a node for these at high adoption levels would be a problem for plebs. Monero seems to offer potential utility in privacy but the doge tradeoff is one of a million coins centralizing node control for txn throughput.
Discussion
How would it be harder to run nodes? Isn't a doggie coin node basically the exact same as a Bitcoin node but with faster block times?
DYOR, monero has more real world transactions than whatever fedcoin you are pushing.
That is just the reality of a cryptocurrency that is used for buying and selling stuff on the streets, rather than being a virtual coin at some binance casino.