Why sObjects can’t be passed as arguments to future methods in Salesforce?

The sObject might change between the time you call the method and the time it executes. In this case, the future method will get the old sObject values and might overwrite them. To work with sObjects that already exist in the database, pass the sObject ID instead (or collection of IDs) and use the ID to perform a query for the most up-to-date record. The following example shows how to do so with a list of IDs.