Why are sn1 reactions important?

${S}_{N} 1$ reactions are important because, as far as we know, they describe a mechanism of organic reactivity, of chemical reactivity. And they describe a BOND-BREAKING PROCESS, as compared to ${S}_{N} 2$ reactions, which are bond-making processes with respect to the rate determining step.
${S}_{N} 1$ reactions are characterized by the loss of stereochemical activity. That is for $C {R}_{1} {R}_{2} {R}_{3} X$, substitution results in the loss of chirality, due to a presumed ""^+CR_1R_2R_3 intermediate.