No, not all katanas have blood grooves. Blood grooves, also known as fullers, are not a standard feature on traditional Japanese katanas. While blood grooves can be found on some modern interpretations or artistic variations of katanas, they are not historically prevalent on traditional, authentic katanas made by skilled swordsmiths.

The absence of blood grooves on traditional Japanese katanas is a result of differences in construction techniques and design philosophies compared to Western-style swords. Traditional katana blades typically feature a smooth, uninterrupted surface without grooves or fullers running along the blade's length.

The focus in Japanese swordmaking is on the meticulous forging, differential hardening, and tempering processes that create a durable, sharp, and resilient blade. The distinct hamon (wave-like pattern) formed during the differential hardening process is often considered a more significant visual feature on traditional katanas.

While there can be variations and exceptions in sword designs, particularly in modern interpretations, it's important to recognize that the absence of blood grooves does not affect the functionality or effectiveness of a traditional katana. The craftsmanship, quality of the steel, and the differential hardening process play pivotal roles in defining the characteristics and performance of the katana blade.