Not really a 'thing of the past since there are still many altcoins out there that had their own client wallet. To be honest, back then I used to think any new altcoin without a proper client wallet is trash and shouldn't invest in. Can't blame me since it was the days where many ERC20 tokens with very lazy and low effort dev so we had to have some standard back then.
But things change and so with some already point out in this thread, the inconvenience and risk of many wallets dwarfed by the convenience on one in many ecosystem.