Some people on here are quite unrealistic about costs. It's not about fancy flowers, even a direct to cremation (so basically no funeral service, just cremation) is over £1000! Cardboard coffins are still expensive as they have to be reinforced to hold a heavy dead body. Even if you have no flowers, a cheap coffin and no funeral cars save the deceased, it will cost you £4000 or more.
No flowers and a cardboard coffin isn't cheap! That's the whole point. The body has to be cared for stored, put in a coffin able to be carried or transported, celebrant paid. Even the most minimal service requires something.
The trouble is that if you don't have anything, and you don't view the body either, it's actually quite hard to realise people are dead. This may not matter if it's a distant aunt who reached 90. Otherwise I can think of situations where having a funeral, which marks out that the person has died, and that they were loved, and what their life meant, is important to at least some of the people left behind (e.g. untimely or younger death).
I thought I wanted a direct to cremation service, but am now thinking it's just a way of further distancing ourselves from death in our culture (which already has difficulties with it) which may be why people then get very depressed/struggle with grief for years but end up having to sit on it and not talk about it too much as it isn't part of our everyday conversations and lives.
I could be wrong though!