1) Free XP is worthless in the idea that you have to play the game anyway to earn some ship xp to convert and you earn a little bit every game. Unless I'm wrong, you can't just directly swap GP into it. So if you're going to play to earn ship xp anyway, why not use the ship that needs it?
Let's say you want the "Survival Instinct" perk from the Onager but hate playing it. It'll take ~80k xp to research it if I recall correctly. So your options are:
Play with it. Even with minimal effort you can earn an average of 2000 xp on Onslaught. 80/2 = 40 games
If you're more than decent or have elite then you can cut that down like butter.
Use what free xp you have but that may not be enough, which brings you back to above ^
Convert xp: which is contingent upon a fully researched ship to use for conversion (which will cost either more ship or free xp to spend!), xp from those ships, and GP. Any of those can run out, which brings you back to above ^
Once again, you have to have some ship xp to use. So 10 games using the Onager = 20k xp, that's already the majority for the 1st module research. A conversion for another ship's 20k xp = 500 GP = $5 US. So if you were able to fully convert all the xp needed then that's $20 (the minimum purchase pack) just to fully research that 1 officer briefing. Using that GP on elite status instead would gain you significantly more than that in not only ship xp but some free xp earned after battles so in the end it's a poor trade off.
2) GP is finite, as in the players do not have an unlimited supply themselves. They can acquire more by buying and/or career progression, but they will always either run out, have an unusable amount, or just stagnate. Since it is not a continuously renewed source or income, it is finite.
3) You may have several rich friends that can burn through thousands of dollars at a whim, but that's not how the majority of the world works, especially when it comes to videogames. A one time $20 purchase is one thing, maybe a little more later, but most people have the ability to set a limit that's not even in the realm of that possibility. So now GP is a precious resource to them and not to be wasted frivolously. But the market is already split into elite status, cosmetics, and hero ships. Adding the mandatory fee for xp conversion is already in a losing position because it's a 1-time trade off unlike the others because they last longer (despite elite being only temporary the gains are immeasurably more than without it). You expect people to constantly be throwing money at the game just to flip xp when regular xp is easy to get? No way. If you are then I either envy your financial status, or I'm sorry that you are a fool. Get whatever period of elite status, play, earn xp, and save some bucks. And just because the option is there doesn't mean people like or want it. I highly doubt people are flocking to the $100 packs.
4) Yes, it pains me to see the points sit there unused, and I'm certainly not going to pay to convert them. Why? Because the xp system itself is not dependent on any purchases of any kind, unlike the other stuff for sale. I earned those points by playing, not through a credit card or trickery. So locking those points only behind an arbitrary paywall just because "it makes money" is flawed logic. In that case, why make the game free to begin with? They could charge up front for everything to make money. $ per ship, $$ per module, $$$ per officer briefing. Then there wouldn't have necessarily been an xp system to criticize. See, flawed logic.
5) Do I need the points? No, I'm getting by fine without them. But it would be better to see them used than not, and I don't see how my asking for a secondary option to convert xp without a fee and at a reduced exchange rate comes off as begging for everything to be free. I certainly didn't say anything close to that.
The game is F2P, and I have no problem admitting that I haven't spent a single penny on it. I've played many such games, and some I've contributed to, while the rest, not at all. This game is in beta, has some glaring problems, and I'm not sure of the future vision yet to determine what my money worth is, especially since I'm not pleased with the current prices of things. If that makes me a cheapskate that's fine with me.