There are too many reasons, why Bitcoin is not a suitable universal currency even for internet, although it is a great thing and a huge step towards society progress.
1. Bitcoin transaction fees are prohibiting for small transactions. There appeared some altcoins which are better for that.
2. Even with Lightning Network and many other existing and upcoming developments, both the tech design and the economic model of Bitcoin won't let billions of low cost transaction per day. There appeared some altcoins which are better for that.
3. Most transactions in Internet require customer protection and hence refundability. And Bitcoin is not great for that. There appeared some altcoins and services which are better for that.
And this list could go on forever, but it is easier to learn about many different use cases of altcoins. For every proper altcoin you can find out the reasons behind it's idea.