Yes, I know some people save tube files as psp and choose the option for PSP 5 and PSP 6 compatibility, but very few people post them on the Web for downloading as psp files, and exporting as a tub file saves the tube in the format used by the version of Paint Shop Pro being used.
I do not save my tube files in PSP format. Mainly because PSP is larger than TUB files. I backup my tubes to ZIP disks and they hold more if my tubes are TUB files.
Archiving [zipping] does NOT always save space either on PSP or TUB files. Most will actually be larger when archived.
This tube sample has these type of byte sizes:
1. cactusbloom.psp = 190,353 bytes.
2. When zipped, it's 190,471.
3. Exported as a tube, cactusbloom.tub = 157,291 bytes, zipped it's 157,437
I zip my tubes for the Web because people expect it. So using the zipped sizes of the psp and tub files, there's a difference of 33,034 bytes. And, folks, that's the size of some smaller tubes!
Considering the huge size of our hard drives these days, it seems I'm nit-picking. But when hosting servers have a limited amount of space for you to use, the saving 33,034 bytes is nothing to sneeze at - especially when you have only 5-50 megabytes for Web sites. And even though I have much more space than that, saving space is an old habit of mine. :)
And not everyone has cable modems, so the smaller the files, the faster the downloads are for those with dial-up Internet access.