European swords historically included a wide range of designs, including both straight and curved blades. However, during the medieval period, straight swords were more prevalent in Europe for several reasons:

1. Thrusting Techniques: Straight swords are well-suited for thrusting techniques, which were commonly employed in European swordsmanship. The straight blade allows for accurate and forceful thrusts, targeting an opponent's vulnerable areas, such as gaps in armor or vital organs.
2. Armor Penetration: Straight swords had better armor-piercing capabilities compared to curved blades. During the medieval period, plate armor became increasingly prevalent, and straight swords were effective at finding gaps in the armor or exploiting weak points, such as joints or visor openings.
3. Evolution of Combat and Tactics: European warfare and combat styles evolved over time. As armor technology advanced, so did the sword designs. Straight swords became favored for their versatility and adaptability to evolving combat tactics, including changes in armor usage and battlefield strategies.
4. Influence of Historical Context and Regions: The prevalence of straight swords in Europe can also be influenced by regional preferences, cultural traditions, and historical developments. Different European regions had distinct sword traditions, resulting in variations in blade design and preference.

It's important to note that while straight swords were common in Europe, curved swords were not entirely absent. Throughout history, various types of curved swords, such as falchions and sabers, were used in Europe, particularly in specific regions or during different time periods.

Overall, the prevalence of straight swords in Europe was shaped by factors such as combat techniques, armor penetration needs, evolving warfare tactics, and regional preferences. The design and use of swords in Europe were influenced by a complex interplay of practicality, cultural context, and historical development.