Some attributes (materials, fills, line styles, etc) are created by library parts, and so the loading of the library re-creates those attributes.
Others are required by ArchiCAD and are re-created.
In general, you would be well to leave most everything alone until you become pretty expert in AC since many attributes that seem 'useless' are used by library parts. Deleting them will result in the lib parts not displaying themselves as intended, requiring more manual setting of parameters than might otherwise be required.
Invariably the next thing someone does after deleting these things is to create new things. But, this can lead to trouble / hassles. AC refers to materials, fills, etc by the internal number that you can see by opening Attribute Manager. If you delete existing attributes and create new ones, you might well end up with the lady in red having a brick dress, carpet face and insulation in section (e.g.).
(Since it will no doubt be something else you are about to do, given that you are in purge mode... do not modify pens 1-10, 19 or 91 as these are all used by the library. Again, once you really understand what's going on, you might change some of these - although 19 must always be white for non-US versions and 91 must always be white in the US version. Safest bet is to leave 19 and 91 as white so that any objects you download from here will display correctly.)
Cheers,
Karl
One of the forum moderators
AC 28 USA and earlier • macOS Sonoma 14.7.1, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB