Everyone knows there are only 2 ways to get a Daytona because its supply is strictly limited: (I am not considering the alternative of putting your name on the waiting list of an authorized dealer and wait for several decades):

1) pay a mark-up of several thousand Euros to get it immediately
2) buy 2 platinum DDs and get one Daytona for free

2) If you own one, the public can conlcude that you are personally known by a dealer which is sort of equivalent to spending a reasonable sum for jewellery on an ongoing basis -> you must be successful in your profession

or
1) You have enough money to spend 8k EUR for a watch which has a retail price of 5.7k. Therfeore, you openly show your disregard for hard-earned money which undoubtedly proves that you are successful in your profession

In conclusion, the only reason is to show-off.