I do a fair bit of yacht racing, and something that becomes important for tactics in yacht racing is know how your boat performs in different conditions. You need to be able to answer questions like:
“With apparent wind-speed of 15 knots, coming from 120° to port, what is my best sail choice, and what speed should I be doing.”
The most important thing here is that you now have a target for the crew to sail for – you know that if you’re not within, say, 10% of your target speed something is wrong and you need to work on your trim, or you’ve got something dangling in the water, or stuck on your keel. Of course, as yachties we often think we have a gut-feel for these sorts of things, but a quantitative answer to the question above is very useful.
In the past I’ve sailed on yachts where the on-board instruments are connected to a laptop, and the it logs the data from the instruments, and presents all sorts of fancy graphs, and some of the more expensive software will certainly give you an answer to questions like the one I asked earlier. However, laptops and water (particularly salt water) don’t mix well at all, and they are not cheap to replace. What’s more, it will take the average weekend warrior an entire season, if not two, to get enough data to start producing useful answers to our questions, and having a laptop on board for all that time is just asking for it to get wet.