They aren't plastic. I send mine for recycling (the pods are 100% recyclable).
Because saying something is simply better for the environment when we don't actually know is misleading.
You've got he impact of production of the pods, the electricity used when using the machine at home, and the recycling process, and all the other hidden processes.
You've got the impact of millions of kettles being boiled for every cup, the plastic/glass/card containers and the production of instant coffee with all hidden processes.
You've got the energy used in coffee machines like yours, the larger quantity of coffee grounds used per cup, the non recyclable packaging and all the hidden processes.
Each process has different possiblites for accidental waste. Damaged pods, or burst/water damaged instant or ground coffee bags. Which products have the largest ruined stock and wasted materials?
Pods could very well be a million times worse. Or they could be on par with ground coffee, but both a lot worse than instant. Or they could be better than one but not the other.
Then there's the ethics involved in production. The sustainability. The price paid to farmers etc.
We simply don't know. You ask why it matters? Because giving out false I formation to further an agenda is wrong. I would like to know the actual answer, but it's not available. You're acting like it is and like your way is guaranteed to be the best. Maybe, but maybe not. So don't judge my choices with no evidence.