As a young man when i first started hunting whitetail i remember these cartridges as being fairly popular. They all were once chambered in a good selection of rifles from numerous manufactures.
What happened to their popularity? Why do only 1 or 2 companies chamber in these calibers?

I can't be 100% sure on this, but I think it has to do with the never ending quest of the "Magnum" cartridges. It's also the same reason why so many hunters now opt for the larger .300 Win Mag and come to a strange conclusion that.... "the 30-06 cannot get the job done anymore" How they have came to this conclusion, I have no Idea.

I personally enjoy the "mild" cartridges. I do own many magnums also, but that does not mean that I think the other rounds are inferior.

I wish the .257 and 6.5's would become popular again and be offered by more gun makers.....but I guess they have to go with the current demand.

The popularity has wained. For a couple reasons. They are a mid length case that usually requires them to be chambered in a long action gun. If buying a long action why not go for a case that has more capacity and thus better performance. A 25-06 over a 257 Roberts, or a 280 Remington over a 7x57 Mauser. Add to that the newer cartridges like the 260 Remington that duplicates the 6.5x55 or the 7mm-08 that duplicates the 7x57 but in a short action rifle. Factory loadings that are kept to lower presures due to older weaker guns also contributed, a handloader can soup them up but if you don't reload your stuck with weak loads. And of course MAGNUM MAINIA is a factor too.

for some reason they thought why sell those when they could sell the .260rem, 7mm-08 etc...?

The .25-06 and .257wby are quite popular in my view, and honestly poor BC's on the .257's lend me to think int he future, more and more guys are gonna being going to the .243's, 6.5mm, 7mm

I think the new big game light kicker is the 7mm-08 , maybe the .243win can join that list too. the 6.5-284 may continue to grow, that offers some speed and ummph without being a true magnum.

The problem I see is everyone wants everything, light kicking, fast/flat shooting, big bullets, and you have to give into 1 or 2 areas to get more of the other... oh and in a lightweight package probably too. whether thats a 7.5lb rifle instead of a 9lb, or if thats a 5lb sheep rifle over a 7.5lb deer rifle...

Although honestly most of us will probably keep 95% of our shots under 300yds, and probably 99% under 400yds, and probably 75% of those would be under 150/200yds, so some of these smaller light kickers as long as you know where your bullet will be at 400yds, can still get the job done well.

The .257 Roberts still has a good following. That cartridge may stick around for some time to come. It has the same nostalgia behind it as the 30-30 does.

What you are seeing now is the cartridge lengths sticking to three overall lengths. There is a manufacturer push for it to save on production costs.

Those lengths are:
You have the long action which is the majority of the tried and true heavier rounds. 270, 30-06, and many others.

The short action which has the 7mm08, 308, 243, and many other calibers.

The super short action, which pretty much only has the 22-250 and 223 calibers of any huge popularity. Both of which are highly popular in my area for predator/varmint hunting. It's amazing, but there are far more options for 22-250 choices than there are for the 7mm08.

IMO, the .243 Win is the reason. The 25-06 does not have much more performance than the .257 Roberts. If I was going to by a .257 rifle today, I think I would go with a .257 Ackley Improved and reload for it. Less powder than the 25-06 and not much difference in performance.

Seems to me from what I've seen at the range, the 6.5 x 55 has a decent following, the 7 x 57 less so but there are a few that keep the ammo off the shelf (she does stock it) and the 257 has enough of a following that she stocks and sells enough that it's on the shelf also. I've got a few 7 x 57 (my favorite is built on a howa action with a shaw barrel) a few 6.5's x 55 (favorite is a vanguard action with a Mcgowen barrel). I think I'd be better off with a 6.5-o6 but haven't made that choice yet and probably won't as long as 6.5 brass is availible. I don't have a 257 roberts, yet that would be a really nice round to try out.

The 6.5 Creedmore is getting some attention. There is a chance that cartridge will become another more readily available option in the US.

I wonder why 6.5mm's aren't popular in the states.Seems like a scenseable round for whitetails,mule deer,pronghorns and a few other big game animals.

I did a little reading some time ago about the 6.5X47......it looks like screamer to me. It had many,many good reviews; but it looks like most guys that use it are going to competitions with it and in a lot of cases doing well with it!