No program is "essential" for simple pipe or pipeline engineering, but some programs are essential when it comes to performing certain calculations related to hydraulics, stress analysis, heat transfer, operational simulations and the like. Some programs are useful for material control, rather than analysis of stresses and hydraulics. Some programs do certain basic things in that regard, ie. simple steady hydraulic analysis, but will not do more advanced calculations, transient analysis, etc. If you could be more specific in expressing your particular needs, you might get a better discussion going.
If it ain't broke, don't fix it. If it's not safe ... make it that way.