Besides, a language for smart contracts that is built around the domain is easier to work with than a general-purpose one. So your Q would then be: why not something like Solidity or similar? - perhaps somebody else can elaborate.
From https://ethereum.github.io/yellowpaper/paper.pdf:
"[The EVM] is a quasi-Turing-complete machine; the quasi qualification comes from the fact that the computation is intrinsically bounded through a parameter, gas, which limits the total amount of computation done."
> By restricting semantics you have finer control over potential slippages.
Solidity have had plenty of "slippages" already and a generally misguiding design, and at least initially was not really into "restricting semantics". Plenty of points made previously, e.g. https://news.ycombinator.com/item?id=14691212.