Innovation is playing offense, not defense
The problem with playing defense - simply defending your existing product lines and market share - is that it is a "static" way of thinking. If we think about traditional "defensive" strategies - in war or in sports - they are meant to prevent someone else from doing something or taking advantage of their strengths. However, most defensive strategies are by their very nature tactical and static - think trench lines, castles in warfare or big defensive linemen in football. These factors mean that the defense is in constant reactive mode, not proactively attacking but intent on defending and making an attack by the offense costly and difficult. Which works as long as the offensive team or army works with the same mindsets as the defensive plan calls for. If the thinking changes and doesn't align with the defensive capability or plan, the defense can be quickly rolled up. I call to your attention the fact that in most wars in the 20th century, the army on the offensive usually won, and even in the cases where that wasn't true (Germany in World War II for instance) they were the aggressor and were winning, just made the mistake of fighting on too many fronts.
The point here is that playing defense becomes a game of what you are willing to concede. It places the organization in a hunkered down, reactive mode where most of the energy is committed to quick reaction to thrusts and attacks. It also assumes that the environmental conditions will remain relatively the same. These concepts were probably reasonable for Fortune 500 companies in the 50s through the 90s. A firm could scale up, put up reasonable defenses and operate in a profitable but defensive posture. All of that changed with NAFTA, the consolidation of Europe and the emergence of China, India and Brazil. Now, we have aggressive competitors intent on offensive engagement who don't necessarily play by the same rules. The pace of change increases and any firm in a defensive mindset is attacked on all sides, as large and small competitors chip away at valuable customers and products.
Meanwhile there is a growing interest in innovation. Innovation is offensive in nature. It assumes there are new markets to address, new customers to reach, new problems to solve. Innovation is proactive - it forces the firm that embraces innovation to change and it forces the firms that are impacted to change as well. Given the fact that innovation requires change, both internally and externally, you can understand why some firms would prefer to play defense rather than offense. Defense in a static environment is fairly safe and predictable, doesn't invite risks and requires little change. Offense, on the other hand, is risky and uncertain. As a famous football coach was quoted about the advent of the forward pass, three things can happen when you throw the football, and two of them are bad.
However, in a market where the pace of change accelerates, and competition increases from every quarter, and the environmental and legislative conditions change constantly, playing defense is exceptionally difficult. Adapting to the changes and anticipating and taking advantage of the changes is paramount. In conditions such as these, you can't simply play defense - you must play offense as well. It used to be said in football that offense brought the crowds but defense won the championships. That may be true in sports but it is not true in the business world. Firms that believe they can survive in these market conditions by defending turf are bound to lose, while those that innovate are more likely to survive and thrive.
Think about the cognitive dissonance associated with the change from a defensive minded approach. In football terms the difference between Mike Ditka and Joe Gibbs. Firms that have been comfortable in a defensive minded approach are fighting off competitors, extending existing products and optimizing their operations. Good defensive approaches ward off competitors, consolidate logistics and build up defenses like patents and other protections. However, they also impede the ability to move quickly and shift direction. Offensive minded organizations tend to seek advantages, are willing to move quickly and address new opportunities. They think on their feet and attack where they have opportunities and advantages. The methods and concepts are radically different, and trying to shift a company from a defensive mindset to an offensive mindset - from business as usual to innovation oriented - is a time consuming but highly necessary process.