There is no “should” just as there is no “standard” in leasing. What I am saying is that this is often the case. How long has the space been vacant? How many people are looking for space? How does the rental rate compare to other options? The kinds of upgrades we are talking about stay behind when you leave. Before I leased a space where I had to pay for those things I would be looking for either space that already has them or a landlord that will pay for them.
Never forget that there are a lot of “money buckets” in a lease. People focus on the base rent and forget the other places where there is either value or expense. Rent increases? Flat, Inflation based? So called “market” (defined how? and what happens if you disagree?) How about a rent holiday? I would not expect to pay rent during construction but most landlords will not give that away unless you ask for it and most attorneys have no idea. (This is why there is place in the world for commercial tenant rep brokers) If your landlord will not give you everything you want/need in TI money, look for other ways to get it like no or low rent rent for some period of time, no rent increases for five years, marketing allowance? If he does not want to pay for build-out and does not have a broker or YOU do not have a broker tell them you want 3% of the total lease value (base rent X entire lease 2000 square feet X $20 per foot X 5 years = 200,000 so that would be $6000) in cash toward build out from the commissions they are saving. Sometimes a LL will give you a good deal, but generally only if you ask! Sometimes you have to get what you need in lots of little pieces.
Of course all this is moot if you are in a hot market with a waiting list for space. But is not the case in very many markets. For example, the most recent business I opened I negotiated the lease in 2007 when the market was pretty hot here. I still got the LL to pay for all HVAC (including maintenance and replacement), lighting allowance of $10 per foot, all utilities to the box inside the space, and no rent for 8 months after they turned over the space to me with all permits in place for my work. On top of that I got $40 per square foot allowance for my improvements. On the other hand, we are in a very prime location and pay high rent.