Telecom organisations take longer to respond to cyberattacks due to the complexity of their networks. They are much more distributed and extended, along with having far more customers connected than other industries. The data they transmit across the network is also massive in size by comparison.
In addition, their core business is to provide a continuity of service. Telcos cannot just cut their network when under attack as other businesses can. This would affect end users that rely on and pay for consistent network availability. Therefore, Telcos must be constantly "up", and ensure service continuity at a much higher scale than enterprise businesses. In the end, it's a matter of scale.