The early days of the game were much like rugby. It is as though during the original game of football, was started as a bunch of guys getting together to play rugby but could not remember the rules, or purposely modified rugby where instead of continuous play, they preferred to start and stop with collision-like starts and ending with 'tackles' (a term used for the same thing in rugby). Rugby advances the ball by running and punting to gain field position, and to score a full touchdown-like score, they must 'touch the ball down' in the scoring area or the end zone.
Decades ago, football decided to add a forward pass that would advance the ball forward so they made up forward pass rules, so thus the beginning of the forward pass.
The kick through the field goal posts was always 3 points and a touchdown worth 4. Decades ago they changed the kick after a touchdown to be worth 1 point and a touchdown 6 points.
Very recently when the USFL (I think it was the USFL) made its bid to compete with the NFL, they found it was more exciting that a play from scrimmage after the touchdown should count as 2. The NFL in one of its moves to keep from losing audience to the rival upstart league, adopted the 2 point scrimmage after touchdown score.
Of the 2 sports, rugby rules are more consistent in it competitive nature, and they even recently adopted replay reviews where the video of the portion of the play being reviewed is played on the same video screen as the spectators see, and the referee is shown watching the same as the spectators. In football, even with the same video screen technology, the referee puts on a headset with access to the NFL's central office in New York, discusses the play with officials in New York, reviews the play under a hood and then emerges with whatever they have discussed with officials in New York. The process many times make the reviews look fixed and/or corrupt.
Between the 2 sports there are many other odd 'similarities' or 'coincidences'. For instance, the ball gets hiked between one players legs to another, the fullback in rugby and quarterback in football. This player receiving the hike then distributes the ball to another player, runs it himself, or in rugby, punts the ball to advance or gain field position.
NFL and college football rules change each year primarily for increases in profit. Sometimes rules are modified for safety, but safety rules are only usually made because if they aren't, the NFL is afraid to lose television and/or attendance ratings. For instance, only after player and fan outcry were rules made to decrease likelihood of head injuries. The NFL in particular has known for decades about serious problems with head injuries, but until the outcry, they refused to change much to prevent them.
In rugby, an unsafe tackle can result in a player being disqualified for the remainder of the game while the disqualified player's team must continue with a player short.
Rugby will enter the olympics again the next cycle. It hasn't been an olympic sport in many many decades. The last country to hold gold as I understand was the USA. I guess the USA team has been champion this whole time.
In the Rugby World Cup held in Japan last month, we (the USA) lost terribly. South Africa won, which was a huge deal to the ethnic minorities in their country because it was the first time they won with a black skin colored captain (they never allowed a black skin colored captain before). My favorite team is the All Blacks, New Zealand's national team because we visited there this summer, but unfortunately putting an All Blacks bumper sticker on my car here in Arizona would likely attract rock throwing, and God knows what else.