That may be true for the author, but it's pretty common to use fixed point integers for DSP. It's less expensive in hardware, and very convenient. You don't need an FPU or a floating point DSP, it's easy to implement in FPGAs (which often have integer adders and multipliers as extra blocks also), and fixed point integer algorithms are pretty easy to characterize in terms of SNR and other tradeoffs (MATLAB has an entire "Fixed Point" toolbox for that, and it's great).

Often in DSP, there is just no good reason to use floating point instead of fixed point integers.

Some CPUs don’t have any floating point support.

Back in the day, this was the case for the ARMv5 CPUs used by a major phone manufacturer and the software JPEG decoder couldn’t use floats. IIRC you only really needed them when doing YUV -> RGB conversions, so that was all done through integer arithmetic instead.