Many people feel that modern caps, particularly film caps, are so good that bypassing is no longer necessary. Bypassing as mentioned is usually done with a cap 1 to 2 orders of magnitude smaller than the initial cap, which is chosen for the coupling frequency requirements.
Some also attribute smearing, etc. to bypassing. Since these I assume are the output coupling caps, I wouldn't think the frequencies to be passed were high enough to worry about (22-30K tops?) and that the 4.7uf cap should pass them just fine. DC coupled would be even better, but I guess not with the tube stage...