I had a set of sliders sat in the garage for 6 years before I sold them. After driving extensive lanes across England and Wales, and 1,000s miles of off-road trails across Europe and Russia, I have never once needed a set of sliders. For the cost of a set of sliders I would imagine there are much better options to spend the money on, or put the money towards a good trip.
I’d say it’s down to personal preference. I wish I could say I’ve never needed rock sliders when I didn’t have them but I have unfortunately, and there’s times I’ve had them where I’ve been pretty grateful for the £600-800 spent. Plus the wife needs a step ladder to get in with after the lift so win, win all round.