Life long Worcester resident who moved to Boston 4 years ago. For context I am a college graduate now in my early 30s and make an above average salary. This is my opinion on the matter, not fact.

My move was 100% for work and lifestyle improvements. Worcester is great but it really doesn't compare to Boston for young professionals especially ones making a high salary in engineering or other fields. There are more jobs in quantity and almost more importantly, the jobs are with more prestigious company's that young professionals want to work for. These company's are the same ones that are going to WPI and other universities in the area and recruiting on campus so the students get internships or jobs through college so the natural progression is to move closer to work. They likely are also going to be making a high salary both due to their profession but also due to the Company's name and location which is most likely in or immediately outside of Boston which is considered a very HCOL area so they dont mind spending a little extra on rent due to the below:

There is simply more to do in Boston and more people in their demographic. I go out in Worcester on occasion with friends, there isnt one bar I've gone to that is comparable to the least crowded boston bar on a Friday. Hell a Tuesday at some of my local places are more filled than Funky Murphy's on a Friday. Combine that with the terrible commute and it makes sense why these individuals are willing to live with roommates or "downgrade" their living situations to make the move. They want to have more options for everything - shopping, dining, going out, entertainment, even the beaches are closer to boston than they are to Worcester.

Worcester is a great city, my fam and friends are largely still in the area and I will always love it and come back often but the lifestyle it is not really comparable to Boston in anyway and staying in Boston will usually lead to more advantageous career paths either through networking or the natural progression from working at prestigious companys.

IMO If worcester really wants to fix the problem one of the big things they need to do is attract more publicly traded company's to setup headquarters here. These Company's typically employ more people and have the brand name and other benefits to retain the students locally. A good example of this would be Unum. They were here for a couple of years and left, and that is a summary of why we cant keep student. This is not to say that private Companys cannot be good employers or employers of many people but simply an example. I am well aware that Hanover is public and is headquartered in the city and that Polar and company's like Math Works in Framingham are both private but seen as generally good employers.