Eipstein was 6 to 8 years their senior, he seemed like a knew it all in entertainment industry. Epstein went to Royal Academy of Dramatic Art (RADA) and the boys thought he couldn't go wrong.
Eipstein and the group made the right decision. I think the fans wouldn’t mind with their leather jackets, but many Rock ’n Roll bands in that era dress up similarly. I believe it wouldn’t make them stand out.
The band’s image in the beginning of their career is important. When every band dressed up similarly, it’s nice (especially for the young female fans) to see four young men with attitude and personalities singing I Wanna Hold Your Hand in suits.
The suit is a nice touch, such a neat way to make an entrance and introduce their music to broader audience.
So, in the beginning of their career, the suits played a significant role but after the music is well known, the fans just like them for their music, not their appearance. They can dress up however they want. This is an image how they evolved in 10 years of their career: