Often it's a lack of real estate for any other interchange. As the interchange is very narrow compared to a partial cloverleaf.
The other option is then a diamond interchange. The diamond interchange is more economical because it doesn't need a particularly wide bridge (4-6 lanes depending on the traffic of the other road).
The single point interchange also has a large conflict area in the middle which is less safe than putting 2 intersections next to each other.
The one major plus is that left-turning traffic from both off ramps of the Highway can go together. The left turning traffic of the other road can go together if a contra-flowing setup is used.