Any VTOL/STOVL jet has to trade off other performance qualities for VTOL/STOVL capability. Likewise, the Gripen still needs a longer runway, which limits the use of “improvised” airfields.
In practice the main benefit of STOVL has been in naval aviation. CATOBAR carriers are expensive and challenging to build, especially if you don’t have the economy of scale of building a dozen of the same class instead of just the 1-2 most countries can actually afford. A STOVL jet can also operate from an amphibious assault ship. The feasibility of the “improvised airfield” concept with modern jets is unproven and controversial, while STOVL naval aviation has been successfully done for decades.
In practice the main benefit of STOVL has been in naval aviation. CATOBAR carriers are expensive and challenging to build, especially if you don’t have the economy of scale of building a dozen of the same class instead of just the 1-2 most countries can actually afford. A STOVL jet can also operate from an amphibious assault ship. The feasibility of the “improvised airfield” concept with modern jets is unproven and controversial, while STOVL naval aviation has been successfully done for decades.