The "best" (read: most accurately made) bullets are not necessarily the "best" (read: applicable design) for the task at hand. Lathe turned solids will ALWAYS be more consistent in at least one dimension than jacketed bullets even when turned on a bent lathe by a blind man. That doesn't mean they are the best tool for every job. Long range needs high BC because of changes in the fluid the projectile travels thru (wind, temp, humidity, etc).
Lathe turned bullets composed of copper weigh considerably less than lead bullets in a protective copper shell. If we could lathe turn solids from a material as dense as lead the would entirely dominant in long rand paper punching.
Hunting bullets sacrifice performance for performance or in other words …there are trade-offs. Bigger open tip, more drag/less bc. Smaller open tip (Berger), higher bc/less reliable expansion.
As far as "All who pay money to compete use the best materials to do it with...." this simply an naive over simplification of life that results an factually inaccurate statement.
Copper has a density of 8.93 g/cm3, Lead is at 11.34 g/cm3 while Gold is 19.30 g/cm/3. So solid gold bullets would be superior ballistically than copper or lead bullets but I don't see anyone shooting those, probably because they aren't "the best material to do it with…". Osmium (22.587 g/cm3) on the other hand would yield the highest BC bullets known to man at twice the weight to size ration of a lead projectile. Haven't seen many people shooting those 6mm 230gr Osmium DTAC's though.
In reality, "All who pay money to compete use the best materials to do it with...."…in a budget! Be it a budget of money or physics or time it is still a budget. There is no reason not to use a 4000x frozen scope for 50yrd benchrest to get THE most accurate crosshair placement possible…except for size, cost, time to acquire target, impracticle use at any other distance or lack of ROI.
It is ALL compromises. Name ANYTHING that is "the best" for "600,800,900,1000,1200 yd.matches" and I can nullify that choice with a better one.
@orkan said it very well. Shooters use what is popular, popular is what people talk about. The more people can afford it the more people that can talk about it. Competition takes repeatition and I don't see many billionaires running "the. Best" anything in matches. There is a reason sponsored shooters use better equipment and consumables than the average shooter and that is simply because the cost to practice and compete goes down.
Rarity, price, availability, time, entry fees, range time, range availability, etc all play into the choice what "All who pay money to compete use the best materials to do it with...."