First off, as pointed out below, making copies of national IDs is illegal in some jurisdictions, but there are many other IDs which according to the issuers may not be copied. Think drivers licenses, library cards, and so on.
That being said, all IDs that I own are issued for a particular service, any app/webservice asking me to upload a copy of them, would most likely re-use some aspect of value that these IDs provide for a different purpose, and I can't think of an actual, compelling reason why I would give someone else access to it.
And that's before even thinking about security and the possibility of a breach.
Would you mind sharing why you are asking ?
