What's your experience with corporate phones? Is this something employees want/need?

This is extremely dependent on expectations and culture. There are some positions that require phones and others that never use phones.  In my role the only calls I get are marketing calls.  I could do without a phone and simply reply on collaboration tools.  

The movement is definitely away from on prem monolithic services (either traditional or voip) to towards cloud/hosted solutions and only for those roles that require phones.

I am happy to get rid of traditional phones across the enterprise and only use collaboration or soft phone capabilities.  One less thing on the desk.

I see that experience with corporate phones significantly depends on the industry and demographics of the employees. Corporate phones in the past were seen as a perk and almost a status symbol (like a company car in some countries). Lately, there was a universal shift towards allowing you to install business apps (Outlook, Teams, etc.) on personal phones. That worked for many people, especially those who were not entitled to or did not want to have a corporate phone. After that, however there was a pushback from IT Security to limit access to corporate data from personal devices, and we seem to be back to square one with the need to carry two phone. Many employees are not comfortable with installing personal and social media apps on work devices, however others are concern about excess data usage of corporate apps on their personal devices. So most corporations still need to do a balancing act regarding BYOD and corporate phones. However this will start changing with massive return to work and wider adoption of hybrid and remote workplaces.    

Corporate phones are good to have. As they give assurance of providing infrastructure and equipment’s to do work efficiently. But all such devices work in benefit of the organization, only when there is some reasonable usage policy implemented. Few organizations provides Corporate phone with MDM solution implemented, which also force employees to go for additional device for their personal usage. I believe a moderate controlled device can be provided with employee, where employee privacy also respected.

For us, yes. It has been working well. All managers or above are assigned with a corporate cell phone. Some lead staff members also do receive corp cell phones based on job functions.

In my experience:
-Most of the Employees want corporate phones. -
-Any one who is providing off hour support needs it. 
- if you enable personal email, Facebook, WhatsApp etc.then they may not have to carry their personal phones 
- if you give them one of the latest phone models they would love ❤️ it
- Some may opt for BYOD but many employees may not like too much ‘intrusion’ on their personal phones.
- it depends on company culture and do people see this as a benefit