It is a given that accounting firms and corporates are not specialist tax software designers/builders, which is why spreadsheets are so common.  Typically these spreadsheets have been handed down in an organisation over the years, with often an error or two that 'everybody knows and works around....'

In the early 2000s, Australian Big4 accounting firms - PWC, KPMG, Deloitte & EY - as well as Moore Stephens (the particular division is now Shinewing) in an effort to create standard processes, reduce risk & exposure within their own business, created a series of bespoke tax tools for usage within their firms and then also made these tools available to their clients. 
With the vast array of clients, these tools cater for all tax situations and it is a rare case that they don't.  By designing the software in a non-spreadsheet environment allows for functionality that shred time and increases accuracy.  In the mid-2000's the change in structure to these accounting firms resulted in the sale of these specialist tools to Thomson Reuters and CCH although Shinewing still own their CTS product.

Why should a corporate tax team use one of these solutions?  Integration of ERP information directly into the tax reporting cuts down manual handling of information for a start.  TEA/Provisions, final tax preparation for review by the auditor/accounting firm is made easier as they use the same tools along with process efficiency, accuracy, consolidation and more.

Why should an accounting firm use these tools? for all of the same reasons above.  Even if you do not have direct access to the ERP system, importing information is easy. If you have a 'special spreadsheet' for a client, you can link the figures directly into the statement of taxable income - neat huh? 
Furthermore, for accounting firms these tools can increase your profitability by reducing write offs and costs.  By automating processes, the tools typically saving anything up to 10 hours for every entity they are used upon: example: 1 consolidated group of 5 entities - that is approximately 50 hours of work saved just in tasks that are now done manually; nothing to do with the tax technical component: this is just in areas such as creation of the tax return, cross-referencing of the working papers, etc the mindless, zero value tasks.  Your staff don't want to do mindless tasks; they want to learn.  That is what these tools also do: teach.

I can see no reason existing for a firm not to utilise functionality guaranteed to improve your turnaround times, reduce your risk and get you home earlier - I'd love to hear if you disagree.  

These tools are no longer ranked as a nice to have - they are now as fundamental to an organisation as the four walls of the building.

It now comes down to the will to change: you could meet each of these vendors and spend many hours sorting which solution is for you and the get the manifold follow up calls and emails and with the potential savings, why not?  Or you can call me to discuss your needs, pre-screen the solution / company based on your needs and get an independent report - especially if you want to be more discreet about learning more about these solutions in a manner that won't result in your phone/email running hot.

Corporate tax is just one area: there are myriad tools available to streamline your tax and financial processes - just ask me.

Over to you - visit my website to choose whether you are a corporate oraccounting firm or if you would like to learn more.

Alan