While those footer links back to the agency that created the website used to be commonplace and sought after, it's shaky ground today--even just one or two no-followed links from a client's site could get you in trouble--in the future.
Today, a followed link or two from the footer of a client's home page and another one from some an interior page (each link having different, non-exact match anchor text) may still provide your site some advantage--and that's the problem. Using those links to your advantage may help your authority in the present but you shouldn't be surprised if that authority is stripped at some point in the future. You know what it looks like when authority is stripped? A penalty.
If you are still getting a followed footer link or two from each of your clients, that shouldn't be your only means of building authority--it should be a supplemental means. You really need to work just as hard as any other site in any other industry to build editorial links back to your site in order that you not suffer an authority adjustment down the road.
The best practice is to nofollow those links in order to prevent them from giving you problems in the future.