Well, one point is purely as a marketing tool. I doubt very few of these lamps will ever last 30+ years, due to moving, accidents etc, and probably dyson doesnt either. however its effective to say that in marketing.

Outside of that, people expect certain pieces of hardware to just 'work' forever. Generally they don't expect a lamp to ever 'require' an upgrade. Yes it will probably be replaced for some reason in that timespan, but not generally due to 'failure'