Kinetic Barrier of ATP
This is not exactly an answer making strong use of references etc. but it does give a good hint. The most ‘energetic’ bonds in ATP are the phosphoric acid anhydride ones i.e. the $\ce{P-O-P}$, which, to hydrolyse ATP, must be attacked by water. The most logical path of attack is one according to the $\mathrm{S_N2}$ mechanism, where a lone pair of water attacks the rear side of a phosphorus-oxygen bond and liberates some phosphate species. ($\mathrm{S_N1}$ can be ruled out, since it would result in a phosphocation which is surrounded by three electron-withdrawing oxygens making the cation highly unstable.)

The problem in this mechanism is physiological pH. It is safe to say that the entire ATP molecule is at least a dianion, if not even a tri- or tetraanion. Now water’s lone pair, i.e. its partially most negatively charged area must approach this already highly negative molecule — but that would result in the repulsion of same charges leading to a high activation barrier.

This would be circumvented by protonation, and indeed even at equilibrium there is a certain probability that a higher number of protons attaches to ATP, making it less negative. This probably helps to account for the slow but steady decay of ATP.