Usually, the one asking that question is simply looking for more ideas. Unfortunately, asking for better ideas can limit other folks from giving potential solutions. By asking for better ideas, it is implied that the first idea was a good one to start with. It can also make folks try to decide if there idea is better than the first one or not. When people worry about whether their idea is better or worse, they might just choose not to share it at all.
A better way to say it, "Thank you! Does anyone have another idea?" No judgment. No comparison. Simply an invitation to get more ideas on the table.