Software vendors (and their cronies) do it for self-serving reasons, but if you have any independent stats to prove your case feel free to share.
https://www.statista.com/statistics/387447/consumer-electronic-devices-by-internet-access-in-the-uk/
"Devices used to access the internet in the United Kingdom (UK) in from 2020
Published by
S. O'Dea, May 25, 2020
Smartphones have pulled away from laptops to become the most important device used to access the internet for close to half of those accessing the internet in the United Kingdom (UK) in 2020. In 2020, significantly more people identified smartphones as their most important device for accessing the internet, compared with those that nominated each of the large display formats combined.
Increasing use of mobile data
As phone displays and mobile data infrastructure improve,
mobile phone users are consuming more data than ever before. From 2015 to 2018, the volume of data consumed in the UK increased from 7.29 million gigabytes to 211 million gigabytes. The
average consumption per sim card has increased from .87 GB to 1.9 GB over the same period. Despite the increase in consumption, mobile service providers have not seen an increase in
revenue from data services, generating 1.73 billion British pounds in 2017, exactly the same amount as they generated from mobile data services in 2010.
Next-gen communications
4G currently offers the fastest means of downloading data using a mobile device, but 5G looks set to blow 4G out of the water in the coming years. Once 5G capable devices are more widely available and more affordable, it is expected that there will be
155 million 5G subscribers in Western Europe by 2024. "
I don't expect you to believe it, but it is fact.
Even in the corporate sector use of smartphone is increasing. G-Suite and Microsoft 365 deliver the means to access the same data from any device regardless.
Incidentally your example calc on a 30,000 userbase for cost of Office SW is misleading. On that sort of userbase the business would be on a Microsoft enterprise plan which would reduce the per capita cost by a huge percentage. In any case, I believe the subscription charge would be totally tax deductible in any current year.
Free software also carries a cost. The cost of providing a machine for each user, the cost of install, the cost of training and the cost of regular updates.
Most users don't need the full range of Office functions, neither do they need the full range of LibreOffice functions, MS do provide a free to use browser version of Office that is fully compatible with the full version and is more than adequate for most basic users in an organisation. There is also the option of the free Google Office apps.
I have nothing against Open source software as such, nor do I have issues with local area network solutions. However, any organisation needs to assess the business need and evaluate software accordingly before deployment.