Because packaging like this usually comes in standard sizes/shapes. Redesigning it to something nonstandard would add costs that the company would probably pass along to you — the consumer.
The inside lining is generally plastic or metallic foils and causes these types of containers to be significantly harder to recycle than if they were made from a single material instead. The only way around this is larger, reusable containers with no waste. 🤷♂️ Not to say you're the problem, just saying that it not being "made of plastic" doesn't really matter as it's still not made of biodegradable materials.
Was gonna say— it’s encouraging seeing cheaper more environmentally friendly packaging like this. Great reuse of existing production machines and materials too. But damn if that label isn’t just very poorly designed for the product category.
That's on purpose. There is some weird marketing trend in France about "feeding" your hair and skin. I guess, it goes also to dishes today. Look for the smoothie-shampoo