i think the age of house is a big factor. it it is an old house there could be all sorts of problems hidden away and a survey gives that extra peace of mind plus the surveyor can be sued if there are expensive problems that he didnt spot.
for newish houses that have nothing visibly amiss,it is a waste of money in most cases
we are moving and our buyers surveyor came out today to check out our 7 year old semi. he had a general poke around , checked that all the windows were opening and closing etc. the most technical thing he did was get us to flush the loos while he looked down the drains to see they werent blocked.
anyone with a short checklist could have done the same thing and saved themselves €500