Videos directly captured from a computer or smartphone screen have certain characteristics that differentiate them from camera-captured (CC) ones. These videos are called screen content (SC) videos whose specific encoder has been introduced as a new extension of the HEVC standard called screen content coding (SCC). Most screen content applications are real-time with low delay requiring an accurate rate control. The difference in the characteristics and use of special coding tools such as palette mode, intra block copy, and adaptive color transform in this standard, have affected the mechanism of bit rate generation and control. This paper presents methods and criteria to evaluate the controllability of the bit rate of SC videos and compare it with that of CC counterparts. Furthermore, the requirements of SC video rate control are studied. The experimental results indicate that the bit rate of SC videos is much less controllable than the conventional ones so that the conventional rate-distortion models and bit rate control algorithms are not effective in coding the SC videos.