The reason the Israelis went for a mortar in their MBTs were to deal with AT teams getting close to them (experiences from the Sinai in 73). E.g it was more defense minded. They have some obvious utility in an urban setting like Lebanon but accuracy would clearly be an issue as the mortar is internally mounted. Operationally speaking, in a resource scarce AFP, a mortar carried by a Simba has a more restricted range of usage than say, dismounted and carried by the mortar team, who can bring to areas and places not accessible by the Simba. It is question whether how the Simba's are deployed and used.
The Israelis have many fantastic technology, but it is important to remember that requirements/doctrine drive technology. They have some unique pieces of kit that were designed for their use that has a limited market elsewhere. The Merk is one example.
However, if you are considering it as a dedicated, mobile mortar system to support the infantry, then it is a different story. In that case, the vehicle confers better mobility advantages for larger caliber systems. Hence you see systems for 82 ~ 120mm calibre (Scorpion, Spear, 2R2M, SRAM)