Theft, loss, or simple misplacement of one wallet shouldn't end the trip. Cash split into 3-4 locations (wallet, money belt, separate hidden pocket, hotel safe) means single failures don't cause crises.
How to split
Daily-use cash in wallet (modest amount). Reserve cash in money belt or inside-the-clothes pocket. Larger reserve in hotel safe. Backup in luggage hidden inside item. Each location independent.
Most travellers never need the reserves. Those who do are very glad they had them. Small preparation cost; potentially trip-saving.