Well if you dont do it you are a candidate to be a statistic for sure. Fuel hose is notorious for breaking down with age and heat as KG says.
In the scheme of things it is cheap to do if you buy all good quality hoses from elsewhere that Rotax. There is plenty of parts that are far better than what Rotax supply. Now you must also replace the fuel pump every 5 years. I didnt think it was that necessary until my mate has had his fail. Luckily he caught it before any drama by always monitoring his engine parameters while flying.