There's a lot of value in learning assembly language, most of it stemming from the requirement that you must know in detail how everything works, or you won't get very far. This has always been true, from the very dawn of digital electronic computing, but from it follows a fair question: Do I really have to know all that?
The fair answer is no. It's possible to write extremely effective programs without having an assembly-level grip on the machine and the operating system. This is what higher-level languages were created to allow: easier, faster programming at a higher level of abstraction. It's unclear how much of today's software would exist at all if it all had to be written entirely in assembly language.
That includes Linux. There are some small portions of Linux written in assembly, but overall the bulk of the operating system is written in C. The Linux universe revolves around the C language, and if you expect to make significant use of assembly language under Linux, you had better be prepared to learn C and use it when necessary.
There is almost immediate payoff: being able to access libraries of procedures written in C. There are thousands of such libraries, and those associated with the Linux operating system are mostly free, and come with C source code. There are pros and cons to using libraries of C functions (as procedures are called in the C culture); but the real reason to learn the skills ...