It has no specific functional purpose. Your colleague may have included it if they were adhering to a specific style guide that recommends that all SELECT queries have explicit WHERE clauses. If an explicit WHERE clause is not provided, the default is to select all rows. Adding a WHERE clause that is always true will have the same effect.
Another way this query could have come about is if it was generated by a code generation tool that always had to write in a WHERE clause due to the way it was written.
for example:
myQuery = "SELECT X FROM Y WHERE " + ConditionMet(data)?" AccountID = '" + AcctId + "'" : "1=1";
This means that if ConditionMet(data) is true, then only return rows where AccountID matches the AcctId you are passing in. If it is false, then return all rows.
Adding a "dummy" 1=1 makes the code generator simpler to write.
Similarly, adding a WHERE clause that is always false (e.g. "WHERE 1=0") will result in zero rows being returned.