Which is fine if you make it regularly. Otherwise it's buying a bag of flour, a block of butter, a bag of oats, and a bag of sugar. So a mix will be cheaper if only doing a one off.
Also requires a little more confidence - could be someone new to making their own food. Or someone who doesn't feel confident 'baking' something right now for various reasons.
Also making a crumble then requires you to use your fingers to mix and crumble it generally. Arthritis in the fingers would make that really painful - even if only a few minutes for your average person.I'm quite sure there are other medical and/or health conditions which would make it trickier.
So a pretty judgemental comment based on one very short list.