The balance between sweet and sour is crucial to the majority of cocktails and consistently producing balanced cocktails is made easier when using sugar...
Realistically, hydrolysis should have very little effect on the sugar in this case. For the scale of time we would typically see making a pint of simple syrup *with only water*, say 20 minutes of boiling, very little of the sugar will hydrolyze. At "100 °C, ...the first-order rate constant for sucrose hydrolysis is about 10^−6 per second". I estimate (20 minutes)x(60 seconds/minute)x(10^-6) = o.oo12 or about 0.1%. cf. https://chemistry.stackexchange.com/questions/116764/how-long-would-it-take-for-sucrose-to-undergo-hydrolysis-in-boiling-water