Good companies invest in their staff.
Technology is a rapidly changing industry - there is always something new to learn. It is much cheaper to keep a current member of staff up to standard than to replace them with a new hire, which costs time and money in recruitment and getting up to speed. Good companies recognize this, and provide their staff with training in whatever technologies they use. It is therefore reasonable for you to hope that your employer will give you time and resources to learn new technologies during work hours.
Not every employer realizes this, they see the obvious cost of providing training and do not recognize the hidden costs of failing to do that. Sadly this is common.
Your employer won't care more about your career than you do - it's your career.
When you first got a developer job, you (probably) didn't turn up on their doorstep saying, "I know nothing about development, pay me while I learn, then eventually I'll do some work for you!". You probably learned how to develop on your own time, maybe as part of full-time education, maybe getting some qualifications (which may have included a degree), before you got the job. You chose your career, and invested in it.
Now, some time later, your current knowledge is not enough. You need to learn more. Although a good employer will help you with this... ultimately, it's you that needs to learn it. This may involve learning on your own time, putting your own energy and resources (time/money/etc.) into it. It is your career, after all. If you don't want to keep up to date with new technologies, your employer may decide to replace you with someone who will. Then, when you are looking for a new job, you may be competing with other candidates who have already learned those new technologies, while you will be left explaining that your former employer didn't give you training so you never did.
Therefore, while both employer and employee should invest in ongoing professional development and learning, whether the employer does this or not, the employee must, or else they will find themselves lacking skills and knowledge that are needed in modern development.