We live in a world where the norm is to grow up, go to school, graduate, go to work, retire, then do what you wanted to do, and then die.
Cruising, believe it or not, is really hard work. Everyday you get up and start exerting a lot of physical effort. Anchors need to be weighed, sails raised, and sheets trimmed. There are many long hours at the helm where you are not able to stop and have lunch, but instead you must work through the hunger until you forget about the fact that you haven't eaten yet today!
This is very demanding on your body, and easy to do when you are young, not so easy when you are older and retired. At this age, you will require the assistance of many technological devices that will mechanize and automate the processes for you. These come at a significant price, and yet are very prone to failure. When equipment that you rely on fails, you then are stuck, and this will incur added costs as you await for parts and repairs.
All in all, cruising when you are older presents additional challenges, and will cost a lot more to carry out. Cruising when you are younger allows you to negate these amenities and lets you rely more on your physical strength to move your yacht.
If you want to explore the world, and do so on a budget that you can afford, it would behoove you to go cruising while you are younger. Yes, you will miss out on work, but you can always work when you get back. Work will always be there waiting for you to return, but your health will not wait for you to be ready.