Makes sense. TESOL certification is an interesting thing as every country/school/program has a different view on it. Domestically speaking, it's unnecessary and I've never heard of an interview committee giving certification any weight over even basic ESL/EFL experience. Internationally speaking, many schools want to say their teachers are certified. It makes their programs seem more qualified even though certification is overrated at best and overpriced at worst. I would reach out to EPIK and TaLK to see what they prefer when it comes to TESOL certification. It definitely won't hurt to get it (unless you overpay), and it is a valued/necessary component of any EFL resume.