Buying Supplies

@guts3745 You don't even need to find supply chests or search forever - just look for barrels that are floating in the water and you are good to go.
These are rather common to find.
Also you don't need to stop by all islands, just search the ones that are part of your voyage anyways. I'm doing OoS missions all the time and I am doing fine despite these missions can cost you the most food items, firebombs and/or cannonballs.

I guess they don't let you buy supplies for gold because that could be disadvantaging newer players. Unless that stuff comes off very cheap.
Also this adds a bit of randomness. Like when you find much supplies you're bound to take longer to bring all that cargo on board and you never know how much or what type you can bring to your ship.
Think about it what happens when the veteran pro crew becomes an unstoppable power train that can fight endless battles and never has to pause for a longer time to collect new supplies because everything can be bought with one click. Another veteran crew can counter this for sure and have a long and tedious encounter until that other ship finally sinks after 2 hours, but good luck for newer players that either don't have the money or don't want to spend it on items they can't even carry over to the next session.

If these supplies would be cheap to buy on the other hand it'd mostly defeat the purpose of collecting or offering any of these for free in the game.

Buying supplies would be a big advantage for players with lots of gold. The newer players wouldn't be able to stock up as well. At most players should be able to buy supply crates to be able to gather supplies quicker.

Really though, you don't need to stock up that much at the outpost. B get a couple runs worth and be on your way. Supplies are everywhere you go. You pass barrels in the water, they are all over the islands, you find supply/cannonball/ fruit crates easily AND rowboats are loaded with supplies.

I'm my opinion, buying supplies is not really necessary

no buying supplies. gathering supplies is a great mini game.

Supplies are already infinite. They never, ever stop spawning.

Supplies (or anything else that gives any kind of advantage) are a no go for Gold sinks. These get proposed often but go against the spirit of the game.

If we want Gold sinks we need to come up with interesting cosmetic only ways to do it (or things that don't give a perceived advantage to playing the game). I proposed one such idea in Feedback related to Grog and how to make a potential Gold sink around that while adding some flavor to the game in a way I don't feel causes an advantage (though open to someone showing me if I am wrong in the thread). Others have proposed removing cosmetic damage from a Ship without the need to Scuttle or Sink via the Shipwright as a possible Gold sink that only leans on the cosmetic side of things.

Other ideas could be trying to add a visual damage system to clothing and item cosmetics through use/damage that can refresh every session but can also be refreshed mid session via the various shops. That would require a lot of work (as they would need to retro fit this to all existing pirate cosmetics), but could lead to an optional Gold sink for the game that is strictly cosmetic.

Those are just a few ideas that might possibly work within the spirit of the game ranging in degrees of complexity from a development standpoint. But certainly don't try and shoot for things like upgrades to things or ways to quickly get more supplies compared to newer players.