In this context, I would like to recommend an article from Sport in History. The article is from a special edition of the journal devoted to sports kit (here). The title of the article is "From Sportswear to Leisurewear: The Evolution of English Football League Shirt Design in the Replica Kit Era". It is difficult to do justice to the article in a short blog post because of the level of detail covered in approximately 40 pages. In addition to the text there are some excellent pictures and stories. The pictures include graphs of data and adverts used during the different eras. For example, Figure 5a present a line graph of the percentage of replica shirts/kit that include (i) sponsor's logo, (ii) club badge, and (iii) maker's logo. There is a superb contrast between the steady increase in shirts carrying the club badge compared to the zero to 100% spike in both logos that occurred during the 1970s. A key to understanding the spikes is a knowledge of the way that the 1968 UK Copyright Act allowed a groundbreaking deal between Admiral and Leeds United. The article explains the chronology.
Much of the article traces the evolution through three phases. The first phase was the child-replica football kit. A key step in this phase was Umbro's 1959 decision to market child-sized kits to individual customers. Prior to 1959, kits were primarily sold to clubs as sportswear. The second phase was the official replica era. One could argue that this era ran from the 1970s to the present (aided by the addition of club and manufacture logos to shirts of all sizes). The third phase is the retro-replica. This phase overlaps with the second phase and is built on the nostalgia amongst many football fans.
One particular part of the article illustrates brilliantly the way things have changed. In 1968/69 the catalogue for Umbro featured the Manchester United and Scotland player Denis Law endorsing the kits of "Manchester United and Scotland, ... eight other leading English clubs, three Scottish clubs and the international kit of England". Would a current Manchester United player be allowed to make such an endorsement? How marketable would a shirt be without the club badge, sponsor's & manufacturer logo, and the name of footballer playing Champions League?