Colonoscopy & Endoscopy Test. Test?

I had my colonoscopy and gastroscopy test done today. The procedure was smooth and completed with no apparent complications. Both reports shows everything is normal (Please see attached) The doctor also explained to me later that everything is ok and my next colonscopy can be done in 20years since I am 32yrs now. However, the doctor also mentioned that he took tissue sample from both tests as a standard practice and will email me the final results in few weeks. I am a little worried about this coz if the report is normal and nothing abnormal observed, what is the need of collecting the biopsies from both endoscopy and colonoscopy test? Overall, my mind is relatively relieved now but I need answers for this question. Thank you!