[Rainger99]

Playing by USGA golf rules is generally slower than casual golf. Here's why:

1. Strict Rule Adherence:
USGA rules require precise procedures, such as taking proper drops (e.g., measuring two club lengths, dropping from knee height), assessing penalties correctly, and resolving rules disputes with officials or playing partners. These steps add time, especially in situations like lost balls, out-of-bounds shots, or hazards, where players must follow formal processes.

2. Etiquette and Order of Play:
USGA rules enforce strict etiquette, such as playing in the correct order (farthest from the hole plays first), waiting for the green to clear before hitting, and maintaining pace-of-play guidelines. This can slow down play compared to casual rounds where players might skip formalities (e.g., "ready golf" where players hit when ready).

In contrast, casual golf is typically faster because:
- Players often forgo strict rules (e.g., taking "gimme" putts, ignoring minor penalties).
- They may play "ready golf" instead of waiting for the correct order.
- There's less emphasis on formal procedures, like dropping precisely or consulting rules officials.
- Groups may skip formalities like marking scores after every hole.

For example, Jordan Spieth's 20-minute delay on the 13th hole at the 2017 British Open (due to a complex drop procedure under USGA rules) would likely have been resolved much faster in casual play, where players might just drop near the original spot and continue.

Data from the USGA indicates that an average 18-hole round in a USGA-sanctioned amateur event takes about 4.5–5 hours for a foursome, while casual rounds often take 3.5–4 hours on similar courses, assuming no major delays. The difference arises from the cumulative effect of rule adherence and stricter etiquette.