The chances of a 3 to 5 person loop joining A and B are much higher than the chance that A will want something directly from B. Multiswap still retains the advantages of an ordinary two-way trade. No money is required. People can use their own time as a currency to buy the services they need. Trading things directly, rather than using money, is fun and satisfying. Knowing that one's services are valued by others boosts confidence.
Friendships can form around barter exchanges.
Barter is not subject to inflation or economic recessions, and is especially useful when unemployment is high, or in economically depressed regions.