There are a few advantage of having 1Gbps internet.
1. Good speed for all the connected device. Esp important if your household have several power users. Of course, your router has to be good as well.

2. When you need to download/upload large files. When you are working with video files, this can be important.

3. Streaming 4K content. Maybe you've have Netflix 4K or even simple YouTube 4K.

4. Never have to worry about space on your console or computer due to games taking up space. Can easily redownload it again within 5 mins.