Just that really. They usually have plain white or brown bread only, no wholemeal or rye or spelt or anything more adventurous.
Too much mayonnaise, not enough ham or cheese between the bread slices, not enough veggie or vegan options. They're expensive too.
Some of Waitrose and M&S sandwiches are OK. Some of their wraps are not too bad but delicious, mouth-watering veggie/vegan sandwiches are hard to find in supermarkets I think.
Oh well, best to make them yourself. Or have salad instead.