Municipal bonds have limited utility. If one is in a state with a high state income tax burden, they can help avoid some tax if you buy munis for that state. Other than that, they tend to have lower returns than bonds with equivalent risk. And while they used to be pitched as lower risk than corporate bonds, I don't think that's a legitimate conclusion these days. See the Jefferson County (Birmingham Alabama) Sewer Bonds....
Bonds of any type are investments for gullible people that are buying the illusion of a guaranteed return. Those people generally have such little financial sense that they don't even realize the resale value of their bond will drop when interest rates rise. Best case for them is their returns manage to be slightly better than the drop in the purchasing power of the eventual return of their principal. The drop in purchasing power is inevitable as inflation continues to degrade it.
When interest rates rise (a safe bet right now considering the relatively low rates nowadays) suddenly they find their guaranteed return looks pretty weak, and the only way out of their investment so they can get into a higher rate bond is to sell the original one at a loss. Either that or continue to hold it and have the buying power of their principal eroded by inflation year after year.
The only reason I wound up owning that bond I had way back when was that I was following the advice of a financial advisor, who as it turned out had a financial incentive in getting people to buy those bonds.