Chemical registration is an essential system to ensure every compound you work with is identified uniquely. This single central source of identity should be used by everyone (and by all other systems) so you never lose track of exactly what compound was tested.
Equally important is the chemical registration’s function to detect and link duplicates: Compounds may come in a different salt form, which could be considered a new batch of the same compound. A good chemical registration system will alert you if you have already tested a compound before you buy more or spend time screening it again in a slightly different form.
So just like a library needs to keep track of its books, you need to organize and track your compounds:
These capabilities are simply not possible if you keep track of your compounds in a flat file (e.g. SD file or a spreadsheet with SMILES strings).