Why should I care about lambda calculus
Your question is a bit like this: &quot;I am a programmer by hobby, and I learned about von Neumann machines. Why should I care about them?&quot; And the answer is: because they're the theoretical model of computing machines that transformed our society.
Your question about the $\lambda$-calculus has a similar, but less grandiose answer. The $\lambda$-calculus was invented before Turing machines as an answer to &quot;what is computation?&quot; In itself it is not terribly practical, but it has been immensly influential in programming. Many programming concepts that we use today originated in the $\lambda$-calculus. Various languages support $\lambda$-calculus to various degrees, but almost all of them are in debt to $\lambda$-calculus to some degree (even the ones that are claimed to be &quot;anti&quot; $\lambda$-calculus).
If you are a hobby programmer, you should learn a programming language with good support for $\lambda$-calculus, as that will give you the joy of actually using the concepts. For instance, you can try one of the following:

Haskell
OCaml
Racket

Many popular languages have partial support for $\lambda$-calculus, which they implement to varying degree. If you know one of them, you could try the functional programming style (which is what $\lambda$-calculus is about), but keep in mind it's not the Real Thing:

Python lambda give rudimentary support for $\lambda$-calculus.
You can try functional programming in Javascript
Java has been retro-fitted with $\lambda$-expressions to give some rudimentary support for $\lambda$-calculus.
C++ has $\lambda$-expressions too.

LISP belongs to this list as well, as it does not have true support for $\lambda$-abstraction.