It's the wrinkles. It means the leather is stretched out. Which means it's been sat on or laid on a lot. Which means the foam padding won't be as fresh as it could be and it won't be anywhere near as comfortable as anyone would want it to be. It might be comfortable to you, it's your own arse-groove you're sitting in, that doesn't mean someone else will find it comfortable. Any sign of excessive use, such as wrinkling, staining or sagging and it's basically knackered and nobody will want it. If someone wants one "for a dog" they'll use their own knackered sofa when its time to buy a new one.
To sell, it needs to be like new, local enough and cheap enough that the ball ache of collecting it is worth it, versus the convenience of having a new one of your chosen design delivered into your living room.
Sofas are possibly even more important for poor people than rich people, they'll be staying home a lot more sitting on it because they can't afford to go out and won't have the budget for other home décor, so a worn out looking sofa that looks like it will be probably dented with someone else's arse-groove and is realistically coming to the end of its life, isn't what they'll choose, especially if they've no means of collecting it - they'll put a nice shiny new one of their choosing on a credit card instead and have the joy of sitting on something brand new that brightens up their living room (and, briefly, their life).
When young and starting out I was gifted some items by various people. I already had my (good quality, solid wood) bedroom furniture and my (perfectly fine) double bed with mattress, plus a small colour TV with integrated DVD player. I could have totally managed with just that while I saved up for everything else.
Of the stuff that I was given "to help me out", with kindness I naively believed, the small stuff like lamps, food bowls etc was fine. Although that's the stuff you can buy very cheaply in the supermarket, so not really necessary for someone to donate to me. The large stuff was complete and utter shite.
A sofa that was fine except the back cushions were squashed flat on one side and the armrest was totally caved in where someone had sat on it and broken the frame.
A single bed (I was an adult, living a one bedroom flat and already had a bed!) with a mattress that had been "cleaned" with some kind of hand held water using device, then wrapped up in cling film "to keep it clean until brought over", which whilst looked fine absolutely stank of mould when unwrapped.
Bedside cabinets I didn't need that were cheaply shoddily made and stained with mould spores on the inside of the drawers.
A mid size TV with a screen that was permanently slightly green, so it wasn't any better than watching black and white.
A washing machine with an internal mould problem that couldn't be cleaned out meaning all my clothes came out smelling of mould and after one month the pump broke and it no longer drained.
All these things I had to pay £10/item for the council to come remove. I could have put that money towards a cheap new sofa and been over halfway there. These people hadn't helped me in any way, they'd just dumped their unwanted and difficult to dispose of items onto me to save themselves the cost of getting them removed. Nobody wants your shite, people. If you don't want it, neither will anyone else, unless perhaps you're just getting rid because you don't like the colour or are moving in with a partner and have duplicate but still good stuff.