I understand that Bitcoin is the gold and Litecoin is the silver
I don't buy that anymore, not since the deluge of coins coming to market in the past few years. Litecoin is still popular, yes, but calling it silver to bitcoin's gold is basically saying it's the #2 coin. Just glancing at Coinmarketcap, it's #5 and I don't think it's anywhere near as popular as a coin like ETH and some of the others. What you said may have been true at one point, but not anymore.
I mean it started as a joke and yet people are using it even though the development is pretty much dead and seeing services starting to support it now make me question their credibility or even their sanity...
Dogecoin has utility as a currency, probably even more so than bitcoin. The transaction fees are much lower and confirmation times are faster. Yeah, it is a joke coin but it does have a hardcore community even if there's no more development going on. It could stay just like it is and continue to be useful to buy and sell stuff with.
All that aside, I'm kinda puzzled as to why Coinbase would add dogecoin. Hell, even Binance doesn't list it (and that's always baffled me). And given how much it's used for gambling, you'd think Coinbase would want to distance itself from it. If I'm not mistaken, you can get your account closed if any funds going out of Coinbase are used in online casinos. Who knows what they were thinking--but I think it's a cool step forward for doge.