Why $p$-adically interpolate?

1.7k Views Asked by At

I'm studying $p$-adic analysis now and particularly $p$-adic interpolation; for example, constructions like $p$-adic $L$-functions (Kubota-Leopoldt style). I'm having some difficulty though, and I'd like to start with knowing what motivates the study. What do you really do with $p$-adic zeta functions and $L$-functions?