Not only in accumulated bet both in single bet, because there are some people who always base on a single bet and they will still end up experiencing lose. So whether accumulated bet or not so far as is gambling, of course luck always play it roll. even if you want to apply the whole gambling skill, You will definitely experience lose one day, so the fact remains that gambling is just a luck based.
You are right in betting no matter how good someone's skills are, of course you will experience defeat and luck is very important to be able to win a bet or many bets that we place and with luck of course we will be able to win the bets we play and when betting we must also be able to have self-control and not bet beyond our abilities so that we do not have problems in terms of finances.
A game may still go against you even though you make a good analysis of the match. Imagine when an underdog lunch a counter attack that lead to there goal till full match ends. Do you even see this in your prediction. Imagine a red card given within the match and many more. Sport betting go along with good analysis and luck.
In a match anything can happen and no matter how good the analysis we have made before placing a bet, it may not go according to our predictions, then we will experience defeat in the bet without having luck in the bet we place, so in betting skills and luck are needed to be able to win the bets we place and with the skills and luck on our side of course we will be able to win the bets we play.